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CYANAMID  -  Manufacture,  Chemistry  and  Uses 


Published  by 

The   Chemical    Publishing    Co. 

Easton,  Penna. 

Publishers  of  Scientific  Books 

Engineering  Chemistry  Portland  Cement 

Agricultural  Chemistry  Qualitative  Analysis 

i     Household  Chemistry  Chemists*  Pocket  Manual 

I  Metallurgy,  Etc.  | 


CYANAMID 


Manufacture,  Chemistry  and  Uses 


BY 


EDWARD  J.  PRANKE,  B.Sc. 


1913 

THE  CHEMICAL  PUBLrSIJiryC^  COMHANY 

EASTOK,  PA.   \  ,    .    .-,  ,.  .  .    ., 


LONDON,    ENGLAND  : 

WILLIAMS  &  NORGATE 

14  HENRIETTA  STREET,  CONVENT  GARDEN,  W.  C. 


.^w^^^ 

'^^i 


Copyright,  1913,  by  Edward  Hart. 


PREFACE. 

This  volume  is  intended  to  be  a  review  of  the  present  knowl- 
edge of  Cyanamid,  particularly  its  chemical  and  agricultural 
properties.  Its  purpose  is  to  render  some  assistance  to  the 
investigator  who  has  neither  the  time  nor  the  library  facilities 
to  enable  him  to  make  a  thorough  study,  yet  who  wishes  to 
broaden  his  knowledge  of  Cyanamid.  Most  of  the  important 
literature  on  this  subject  is  written  in  foreign  languages,  and 
many  valuable  papers  occur  in  journals  not  found  in  the  ordi- 
nary agricultural  or  chemical  library.  Moreover,  the  opinions 
that  have  been  expressed  on  almost  every  phase  of  the  be- 
havior of  Cyanamid  are  so  diversified  and  frequently  so  deeply 
buried  in  controversy  that  the  casual  reader  is  at  a  loss  to 
know  what  to  accept  as  generally  established  facts.  It  is  hoped 
that  the  present  volume  will  give  to  the  reader  a  consistent  ex- 
planation of  Cyanamid  that  will  form  the  starting  point  for  the 
acquisition  of  further  knowledge. 

In  order  to  arrive  at  an  understanding  of  the  principles 
underlying  particular  phenomena  it  is  necessary  to  adopt  at  the 
beginning  of  an  investigation  some  sort  of  working  hypothesis 
that  will  account  for  the  observed  facts.  Every  further  fact 
that  is  acquired  must  then  verify  the  original  hypothesis  or  the 
latter  must  be  modified  to  fit  the  facts.  The  constant  re- 
modeling of  ideas  to  agree  with  observed  facts  finally  leads  to  a 
system  of  knowledge,  in  which  every  fact  explains  to  a  cer- 
tain extent  every  other  fact,  and  in  no  case  contradicts  any  of 
them.  Such  a  system  of  knowledge  of  Cyanamid,  it  is  be- 
lieved, is  now  at  hand.  The  pure  chemistry  of  Cyanamid,  its 
physico-chemical  action  in  the  soil,  its  biological  behavior,  and 
its  agricultural  properties,  as  presented  in  this  volume,  are  con- 
sistent with  each  other.  Such  consistency  is  believed  to  induce 
confidence  in  the  validity  of  the  views  expressed.  Further 
experiments  may  make  necessary  some  slight  changes,  but  the 
general  scheme  of  the  properties  of  Cyanamid  may  now  be  con- 
sidered as  quite  definitely  established. 

273410 


IV  PREFACE 

There  is  no  question  but  that  Cyanamid  will  play  an  import- 
ant part  in  the  future  development  of  agriculture,  and  that  a 
great  deal  of  research  will  be  undertaken  to  broaden  the  knowl- 
edge of  its  practical  application.  Much  labor  has  been  wasted 
in  the  past  by  the  pursuance  of  faulty  methods,  and  a  great 
deal  of  work  has  been  but  the  duplication  of  earlier  efforts, 
and  has  contributed  little  that  was  not  known  before.  If  the 
publishing  of  this  book  will  direct  research  into  the  fields  that 
still  remain  more  or  less  unexplored,  and  if  it  is  helpful  in 
avoiding  the  errors  of  past  investigations,  its  purpose  will  have 
been  accomplished. 

NashviIvLK,  Tenn. 
January,  1913. 


TABLE  OF  CONTENTS. 


PAGE 

Preface iii 

CHAPTER  I.     Discovery  and  Manufacture  of  Cyanamid  ...  i 

History  of  Technical  Process i 

Nomenclature  of  Cyanamid  Industry 3 

Manufacture  of  Commercial  Cyanamid 4 

Preparation  for  Use  as  a  Fertilizer 7 

Commercial  Derivatives 8 

CHAPTER  II.    Preparation  and  Properties  of  Cyanamide  10 

Preparation 10 

Properties    11 

Action  of  Heat 1 1 

Action  of  Acids 12 

Action  of  Alkalies 12 

Action  of  Oxidizing  and  Reducing  Agents 13 

Other  Reactions 13 

Metal  Salts   13 

Dimetal  Salts 13 

Calcium  Cyanamide  14 

Acid  Calcium  Cyanamide "    14 

Basic  Calcium  Cyanamide    16 

Calcium  Cyanamide  Carbonate 16 

Silver  Cyanamide 17 

DICYANDIAMIDE 17 

Dicyandiamidine 18 

CHAPTER  III.    Anai^yticai,  Methods    19 

Determination  of  Total  Nitrogen 19 

Determination  of  Cyanamide  and  Dicyandiamide 20 

Caro  Method 20 

Brioux's  Modified  Caro  Method 21 

Determination  of  Urea 22 

Identification  of  Amidodicyanic  Acid 23 

Identification  of  Ammeline    23 

CHAPTER  IV.    Storage  of  Cyanamid 24 

Factory  Test  on  Large  Scale 24 

Test  of  Two  Bags 25 

Chemical  Changes  in  Storage 28 

Relative  Amounts  of  Decomposition  Products 29 

CHAPTER  V.    Decomposition  of  Cyanamid  in  the  Soii, 32 

Factors  Involved 32 

Experiments  of  Ulpiani 32 

Experiments  of  Kappen 34 

First  Stage  of  Decqpiposition 37 

Second  and  Third  Stages  of  Decomposition 38 

Influence  of  Concentration 40 

Influence  of  Temperature 43 

Influence  of  Soil  at  ioo°C. 43 


VI  TABLE   OF   CONTENTS 

PACK 

Nature  of  Products  formed  in  Soil  at  Ordinary  Temperatures.  44 

Effect  of  Changing  Ratio  of  Liquid  to  Soil 46 

Influence  of  Aeration 47 

Influence  of  Electrolytes 48 

Nature  of  Effective  Soil  Constituents 48 

Effect  of  Zeolites 49 

Effect  of  Carbon 50 

Experiments  with  Natural  Colloids 51 

Experiment  with  Sterilized  Soil 56 

Conclusions 57 

CHAPTER  VI.    RETENTION  OF  Cyanamid  Nitrogen  in  Soil..  60 

CHAPTER  VII.    Nitrification  of  Cyanamid  Nitrogen 62 

CHAPTER  VIII.    Toxicity  of  FertiTvIzers 65 

Meaning  of  '*  Poison  "  65 

Conclusions  of  Dr.  Paul  Wagner 66 

Other  Explanations  of  Toxic  Action 73 

Dicyandiamide 74 

Formation 75 

Decomposition 75 

Conversion  in  Soil 77 

Pure  Substances  and  Toxicity 80 

Conclusion 82 

CHAPTER  IX.    AGRICUI.TURAI.  Use  of  Cyanamid 83 

Fertilizer  Tests 83 

Use  as  a  Weed  Destroyer - . .  86 

Directions  for  Application  as  Fertilizer 87 

Use  of  Complete  Fertilizer  Mixtures 89 

CHAPTER  X.    Making  Fertii^izer  Mixtures  With  Cyanamid  90 

Mixtures  with  Ammonium  Salts 90 

Mixtures  with  Acid  Phosphate 91 

Other  Mixtures 93 

Advantages  of  Cyanamid  in  Fertilizer  Mixtures 93 

Drying  Action 93 

Preventing  Loss  of  Nitric  Nitrogen 93 

Preventing  Bag-rotting 94 

CHAPTER  XL    Permanganate  Avaii^ability  of  Cyanamid..  95 

Solubility  on  Filter 95 

Solubility  in  Plasks 96 

Rate  of  Solution  in  Flasks 96 

Neutral  Permanganate  Method 96 

Alkaline  Permanganate  Method 97 

Modified  Alkaline  Permanganate  Method 98 

CHAPTER  XII.     Fire  and  Water  Hazard  of  Cyanamid 102 

Test  for  Flammable  Gases 102 

Spontaneous  Heating  Tests 102 

Test  with  Water 103 

Acid  Tests T03 

Behavior  of  Product  when  Heated 104 

Test  with  the  Oil  Used 104 

General  Behavior  when  Treated  with  Water 105 


CHAPTER  I. 


Discovery  and  Manufacture  of  Cyanamid. 


The  problem  of  the  artificial  fixation  of  atmospheric  nitro- 
gen has  engaged  the  attention  of  scientists  for  the  greater  part 
of  a  century.  The  rapid  growth  of  the  fertilizer  industry  that 
has  attended  the  development  of  agricultural  science,  and  the 
great  increase  in  the  number  and  extent  of  chemical  industries, 
during  the  past  fifty  years,  have  emphasized  the  necessity  for 
artificial  methods  of  maintaining  and  increasing  the  world's 
stock  of  combined  nitrogen.  One  of  the  influences  that  stim- 
ulated immediate  action  was  the  introduction  in  1887  by 
MacArthur  and  Forest,  and  at  about  the  same  time  independ- 
ently by  Siemens  &  Halske,  of  Berlin,  of  the  cyanide  process 
for  leaching  gold  and  silver  from  their  ores.  This  discovery 
produced  a  strong  demand  for  cyanides,  which  had  hitherto 
been  used  to  the  extent  of  only  a  few  hundred  tons  a  year, 
principally  in  the  dye-industry  and  to  a  smaller  extent  in 
electroplating. 

Attempts  had  been  made  early  in  the  nineteenth  century  to 
bring  about  the  direct  synthesis  of  cyanogen  from  atmospheric 
nitrogen  and  carbon.  Among  other  processes,  that  worked 
out  in  1847  by  Bunsen  and  Playfair,  in  which  barium  car- 
bonate was  heated  in  an  atmosphere  of  pure  nitrogen,  seemed 
promising,  but  did  not  prove  to  be  commercially  successful. 
The  introduction  of  the  electric  furnace  in  1894  by  Moissan 
and  by  Willson,  for  the  production  of  carbides  on  a  large 
scale,  afforded  a  new  instrument  for  further  research.  Siemens 
and  Halske,  among  others,  at  once  adopted  the  use  of  the  elec- 
tric furnace  for  the  working  out  of  the  problem  of  nitrogen  fixa- 
tion. In  1895,  they  worked  on  the  process  of  Prof.  H.  Meh- 
ner,  which  consisted  in  fusing  a  mixture  of  sodium  carbonate 
and  carbon  and  conducting  nitrogen  through  the  hot  mass.  In 
the  same  year  they  took  up  the  process  of  Prof.  Adolph  Frank 
and  Dr.  Nicodem  Caro,  which  consisted  in  subjecting  a  mix- 


2  CYANAMID — MANUFACTURE:,    CHEMISTRY   AND    USES 

ttire  of  barium  carbide,  sodium  hydroxide,  potassium  hydroxide 
and  carbon  at  a  high  temperature  to  the  action  of  steam  and 
nitrogen.  Frank  and  Caro,  with  the  co-operation  of  F.  Rothe, 
found  in  1895  that  dry  nitrogen  is  essential  to  successful 
absorption. 

In  1898  it  was  found  that  when  barium  carbide  is  heated  to 
a  temperature  of  7CX)°  to  800°  C,  in  the  presence  of  nitrogen, 
about  30  per  cent,   of  the  carbide  is  changed   into  barium 
cyanide  and  the  remainder  into  barium  cyanamide.     The  re- 
actions can  be  represented  by  the  following  simple  equations: 
BaC,  -f  N,  =  Ba  (CN)„ 
Ba(CN),  =  BaCN^  +  C. 
Since  it  was  desired  to  have  all  the  nitrogen  in  the  form  of 
cyanide,  further  operations  were  necessary.     The  product  of 
the  above  reactions  was  fused  with  soda,  when  the  carbon 
again   reacted  with  the  cyanamide  group  and  produced  the 
cyanide  form.     The  cyanide  was  leached  out  with  water,  and 
treated  with  ferrous  carbonate  to  form  the  f errocyanide,  which 
was  sold  as  such  or  fused  with  sodium  to  form  pure  sodium 
cyanide.     The  barium  carbonate  residue  was  again  used  to 
produce  barium  carbide,  as  represented  by  the  reactions : 
BaCOj  -f  heat  =  BaO  -f  CO^, 
BaO  +  3C  =  BaC,  +  CO. 

The  fall  in  the  price  of  cyanides  due  to  the  interruption  in 
the  production  of  gold  during  the  Boer  War  in  South  Africa 
made  it  necessary  to  seek  cheaper  methods  of  manufacture. 
It  was  found  that  calcium  carbide  could  be  manufactured  at 
less  cost,  and  also  had  the  advantage  of  possessing  a  lower 
molecular  weight.  This  carbide  required  a  temperature  of 
from  1,100°  to  1,200°  C.  for  the  absorption  of  the  nitrogen,  but 
combined  it  entirely  in  the  form  of  calcium  cyanamide,  without 
the  formation  of  any  cyanide.  By  fusion  with  alkaline  salts, 
however,  the  cyanamide  form,  in  the  presence  of  carbon, 
readily  goes  over  to  the  cyanide  form,  which  can  be  leached 
out  with  water,  if  desired,  and  be  further  purified.  When 
sodium  chloride  is  used  as  the  fluxing  agent,  the  resultant  mass 


CYANAMID — manufacture:,    CHEMISTRY    AND    USES  3 

contains  about  30  per  cent,  sodium  cyanide,  and  is  known  as  a 
"surrogate."  It  is  suitable  for  use  directly  for  the  extraction 
of  gold  ores. 

Agricultural  experiments  with  the  crude  calcium  cyanamide 
showed  that  this  material  is  suitable  for  use  as  a  nitrogenous 
fertilizer,  and  patents  were  issued  in  1910  to  Dr.  Albert  R. 
Frank,  son  of  Prof.  Adolph  Frank,  and  to  Herman  Freuden- 
berg,  a  co-worker  of  A.  R.  Frank,  protecting  the  use  of 
Cyanamid  for  this  purpose.  The  basic  patent  protecting  the 
process  of  manufacture  of  Cyanamid  was  issued  to  Prof. 
Adolph  Frank  and  Dr.  Nicodem  Caro  in  1908. 

The  large  demands  of  agriculture  for  cheap  nitrogenous 
fertilizer  materials  have  directed  the  efforts  of  the  manu- 
facturers toward  the  production  of  Cyanamid  rather  than  of 
cyanides  and  other  derivatives.  At  present,  the  total  output 
of  sodium  cyanide  derived  from  Cyanamid  is  only  about  2,000 
tons  per  annum,  all  made  in  Germany,  while  the  world's  pro- 
duction of  Cyanamid  is  estimated  at  about  120,000  tons  per 
annum.  The  factory  of  the  American  Cyanamid  Company, 
at  Niagara  Falls,  Canada,  now  has  a  capacity  of  30,000  tons 
per  annum,  and  extensions  now  under  way  will  increase  this  to 
60,000  tons  per  annum.  There  are  thirteen  Cyanamid  factories 
abroad,  located  in  Germany,  Italy,  France,  Switzerland, 
Austria,  Norway,  Sweden  and  Japan. 

NOMENCLATURE  OF  CYANAMID  INDUSTRY. 

With  the  development  of  the  Cyanamid  industry  there  has 
grown  up  a  nomenclature  that  is  often  confusing  to  the  un- 
initiated. The  terms  here  defined  will  be  understood  to  have 
the  following  meanings  throughout  this  treatise: 

Lime -nitrogen. — Crude  calcium  cyanamide,  ground  to  a  fine 
powder  after  removal  from  the  ovens  in  which  it  is  formed. 
It  contains  about  55  ptv  cent,  of  calcium  cyanamide,  CN.NCa, 
about  2  per  cent,  calcium  carbide,  and  about  20  per  cent,  of 
free  calcium  oxide. 


4  CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

Cyanamid. — This  is  a  trade  name  for  the  completely  hydrated 
material  prepared  for  use  as  a  fertilizer  in  the  United  States. 
It  contains  about  45  per  cent,  calcium  cyanamide,  27  per  cent, 
calcium  hydroxide  and  no  carbide.  The  name  is  always 
capitalized  and  has  no  final  "e." 

Cyanamide. — The  compound  represented  by  the  formula 
CN.NHo.  It  is  sometimes  referred  to  as  acid  cyanamide,  or 
free  cyanamide. 

Calcium  Cyanamide. — The  chemical  compound  of  the  for- 
mula CN.NCa,  or  CaCNa,  as  it  is  freqently  written. 

Calcium  Cyanamid. — The  name  used  by  the  United  States 
Department  of  Agriculture  and  by  some  State  Departments  of 
Agriculture  to  designate  commercial  Cyanamid.  It  is  some- 
times used  to  indicate  the  substance  represented  by  the  formula 
CN.NCa,  but  for  the  sake  of  clearness  the  compound  CN.NCa 
will  be  called  calcium  cyanamide  in  the  present  paper. 

Nitrolim. — The  trade  name  for  the  material  sold  in  England 
for  agricultural  purposes.  It  is  a  lime-nitrogen  to  which  has 
been  added  just  enough  water  to  destroy  the  carbide.  Practi- 
cally all  the  free  lime  is  present  as  calcium  oxide. 

Kalkstickstoff. — The  commercial  material  manufactured  in 
Germany  for  use  as  a  fertilizer.     It  is  similar  to  nitrolim. 

Stickstoffkalk. — A  crude  calcium  cyanamide  made  by  nitri- 
fying a  calcium  carbide  which  contains  about  10  per  cent,  of  cal- 
cium chloride.  Its  manufacture  in  Westeregeln,  Germany, 
under  the  Polzeniusz  patents  was  discontinued  in  1910. 

Calciocianamide. — The  Italian  commercial  product,  com- 
pletely hydrated. 

Cyanamide  de  calcium. — The  French  commercial  product, 
completely  hydrated. 

MANUFACTURE  OF  COMMERCIAL  CYANAMID. 

The  first  step  in  the  manufacture  of  Commercial  Cyanamid 
is  the  preparation  of  calcium  carbide.  This  is  brought  about 
in  the  usual  manner  by  fusing  in  an  electric  furnace  a  mixture 
of  lime  and  coke  in  accordance  with  the  following  equation : 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES  5 

CaO  +  3C  ---  CaC,  +  CO. 
The  carbide  is  removed  from  the  furnace  at  regular  inter- 
vals, is  cooled,  crushed  to  a  fine  powder,  and  packed  in  the 
nitrifying  ovens.  These  are  cylindrical,  perforated  steel  cans, 
set  in  heat-insulated  brick  ovens.  A  carbon  pencil  through 
the  axis  of  the  can  is  used  to  heat  the  carbide  to  the  combining 
temperature.  On  admission  of  the  nitrogen  to  the  cans  the 
following  reaction  takes  place : 

CaC,  +  N,  ^  CaCN,  +  C. 

This  reaction  is  accompanied  by  an  evolution  of  heat  which 
is  just  about  sufficient  to  maintain  the  mass  at  the  combining 
temperature.  The  commercial  calcium  carbide  used  contains 
about  20  per  cent,  of  impurities,  which  so  influence  its  physical 
and  chemical  properties  that  the  absorption  of  nitrogen  takes 
place  very  readily  at  atmospheric  pressure  at  a  temperature  of 
about  1,100°  C.  The  addition  of  catalytic  agents,  principally 
haloids,  suggested  by  various  investigators,  is  not  necessary  for 
the  fixation  of  nitrogen,  since  the  manufacturer  can  easily 
regulate  the  reactions  by  suitable  disintegration  of  materials 
and  by  other  mechanical  means. 

Nitrogen  is  obtained  either  by  fractional  distillation  of 
liquid  air,  or  by  means  of  the  copper  oxide  process.  In  the 
latter,  air  is  passed  through  a  red-hot  mass  of  finely  divided 
copper,  suspended  in  asbestos  or  other  inert  material.  The 
copper  combines  with  the  oxygen  and  allows  the  nitrogen  to 
pass  through.  The  copper  oxide  is  easily  recovered  for  use 
by  reduction  in  situ  with  a  suitable  gas,  such  as  natural  gas. 

The  nitrogen  used  must  be  pure  and  dry,  otherwise,  at  high 
temperatures,  there  is  destruction  of  the  carbon  pencils,  and 
of  calcium  carbide,  according  to  the  following  reactions : 

C  +  O  -->  CO, 
C  +  CO.,  —  2CO, 
•c-f  H,0— CO+  H„ 
H,0  +  CaC,  —-  CaO  +  C,H„ 
3O  -I-  CaC,  —  CaO  +  2CO. 


6  CYANAMID — MANUFACTURE,    CHE:MISTRY    AND    USES 

Carbon  dioxide  also  destroys  the  calcium  cyanamide  with 
formation  of  calcium  oxide,  carbon  monoxide  and  free  nitro- 
gen. 

The  reaction  by  which  calcium  cyanamide  is  formed  is 
reversible : 

CaC,  +  N,  =  CaCN,  +  C. 

The  temperature  of  reversal  at  atmospheric  pressure  varies 
greatly  with  the  composition  of  the  carbide  used.  Thus  the 
temperature  of  reversal  lies  at  about  1,360°  C.,^  for  a  crude 
calcium  cyanamide  containing  21.1  per  cent,  combined  nitro- 
gen, and  made  from  a  commercial  carbide  of  the  following 
composition : 

Per  cent. 

CaCj 82.30 

C 1.20 

CaO 14.72 

CaSi 0.06 

CagPj    0.07 

CaS 0.13 

Ferrosilicon - o,  72 

Not  determined 0.80 

An  increase  of  the  free  lime  in  the  carbide  greatly  lowers 
the  critical  temperature.  Thus  with  a  carbide  containing  75 
per  cent.  CaQ  the  equilibrium  point  lies  at  about  1150°  C.^ 

The  effect  of  nitrogen  pressure  on  the  equilibrium  point  has 
been  investigated  by  M.  Thompson,  who  found  that  the  tem- 
perature at  equilibrium  varies  directly  as  the  pressure.^  Since 
calcium  cyanamide  is  decidedly  volatile  at  the  equilibrium  tem- 
perature, even  as  low  as  1,050°  C,  and  distils  to  the  colder 
parts  of  the  apparatus  the  determination  of  the  equilibrium 
conditions  is  open  to  some  errors,  but  these  may  not  be  large 
enough  to  vitiate  the  general  conclusions  that  have  been  drawn. 

It  is  owing  to  the  reversibility  of  the  reaction  that  nitrogen 

^  Caro,  Cheni.  Trade  Jour.,  1909,  p.  622. 

2  LeBlanc  &  Eschmann,  Zeit.  fiir  Elek.,  1911,  17,  20-34. 

^  Thompson  &  Lombard,  Met.  and  Chem.,  Eng.,  1910,  617,  682. 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES  7 

cannot  be  absorbed  by  liquid  carbides  as  the  latter  leaves  the 
furnace,  since  calcium  cyanamide  cannot  exist  at  the  tempera- 
ture of  liquid  carbide.  As  the  carbide  cools  it  becomes  practi- 
cally impermeable  to  gases  and  absorption  takes  place  only  on 
the  surface  to  a  slight  depth. 

Processes  for  the  nitrifying  of  a  heated  mass  of  lime  and 
coke  have  not  been  commercially  successful. 

The  energy  consumption  for  the  fixation  of  one  ton  of  nitro- 
gen as  calcium  cyanamide  is  about  three  horse  power  years, 
including  the  manufacture  of  the  carbide  and  all  subsequent 
factory  operations. 

PREPARATION  FOR  USE  AS  FERTILIZER. 

Cyanamid  finds  its  principal  use  in  agriculture,  as  a  source 
of  nitrogenous  plant  food,  and  for  this  reason  practically  all 
the  crude  calcium  cyanamide  is  converted  into  a  form  more 
suitable  for  its  incorporation  in  complete  fertilizers.  To  this 
end,  water  is  added  to  the  crude  material  in  a  rotating  cylinder ; 
the  one  or  two  per  cent,  of  calcium  carbide  is  decomposed  and 
the  lime  slaked.  This  powdered  Cyanamid  is  converted  to 
granulated  Cyanamid  as  follows:  A  small  amount  of  water 
is  mixed  with  it,  and  the  damp  material  is  run  through  brick 
presses.  The  resulting  bricks  harden  rapidly,  and  are  stored 
until  the  material  is  to  be  shipped,  when  they  are  run  through 
a  series  of  crushing  rolls  and  screens.  The  coarse  material, 
which  passes  through  a  15-mesh  standard  screen  and  over  a 
60-mesh  standard  screen,  is  practically  free  from  dust,  and 
is  known  commercially  as  Granulated  Cyanamid.  The  fine 
material,  mostly  smaller  than  60-mesh,  is  either  incorporated 
with  fresh  powdered  Cyanamid  and  again  run  through  the 
brick  presses,  or  it  is  mixed  with  several  per  cent  of  an  odor- 
less oil  to  reduce  the  dustiness,  and  is  sold  without  further 
treatment.  Both  grades  of  Cyanamid  are  packed  in  ordinary 
fertilizer  bags,  and  are  distributed  in  carload  lots  to  manu- 
facturers of  mixed  fertilizers.  Material  so  prepared  contains 
nitrogen  equivalent  to  18  to  20  per  cent,  of  ammonia,  and  is 
2 


8  CYANAMID MANUFACTURE,    CHEMISTRY    AND    USES 

sold  on  the  basis  of  its  nitrogen  content,  as  determined  by 
analysis. 

The  following  is  a  typical  analysis  of  commercial  Cyanamid, 

Per  cent. 

Calcium  cyanamide  CaCNj  45-92 

Calcium  carbonate CaCOj  4.04 

Calcium  sulphide CaS  1.73 

Calcium  phosphide CagPj  0.04 

Calcium  oxide,  free  CaO  — 

Calcium  carbide CaCg  — 

Calcium  hydroxide Ca(OH )2  26.60 

Free  carbon C  13.14 

Iron  and  alumina R2O3  1*98 

Silica SiOj  1.62 

Magnesia    MgO  0.15 

Combined  moisture —  3.12 

Free  moisture HjO  0.35 

Undetermined  —  1.31 

100.00 

COMMERCIAL  DERIVATIVES. 

Ammonia. — Steam,  at  a  high  temperature  and  pressure,  con- 
verts calcium  cyanamide  quantitatively  into  calcium  hydroxide 
and  ammonia,  thus  forming  a  convenient  source  of  ammonia 
for  the  manufacture  of  ammonium  salts.  The  carbon,  which 
is  in  the  form  of  graphite,  and  the  lime,  can  be  used  over  again 
for  the  production  of  carbide. 

Nitric  Acid. — By  the  Ostwald  process,  ammonia  can  be  oxi- 
dized to  nitric  acid,  mixtures  of  thoria  and  ceria  being  used  as 
catalyzers.  No  external  supply  of  energy  is  required  in  this 
process. 

Cyanides. — When  calcium  cyanamide  and  carbon  are  fused 
together  with  alkaline  salts,  in  the  absence  of  carbide  the  cal- 
cium cyanamide  is  converted  into  calcium  cyanide: 

CaCN,  -h  C  —  Ca(CN),. 
The  product  of  this  reaction  is  called  a  "surrogate."  It  is  used 
in  the  recovery  of  metals  by  the  cyanide  process. 

The  above  reaction  is  completely  reversed  in  the  presence 
of  carbides,  hence  their  absence  is  imperative  in  this  process. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES  9 

Dicyandiamide. — This  derivative  is  easily  prepared  by  leach- 
ing the  crude  calcium  cyanamide  mass  with  hot  water,  pre- 
cipitating the  lime  in  the  filtrate  with  carbon  dioxide,  and  con- 
centrating the  filtrate.  Dicyandiamide  is  used  in  the  dye  in- 
dustry, and  also  as  a  deterrent  in  nitro-explosives,  in  place  of 
ammonium  oxalate. 

Other  derivatives,  such  as  urea,  guanidine,  nitro-guanidine, 
are  being  made  at  the  Spandau  works,  in  Germany.  A  process 
has  also  been  worked  out  for  the  production  of  synthetic  indigo 
by  the  action  of  dialkylcyanamides  on  Phenylgycine  and  its 
derivatives. 

Ferrodur  and  intensit  are  special  mixtures  prepared  for 
metallurgical  purposes.  Ferrodur  is  a  cementing  powder  used 
in  place  of  potassium  cyanide  for  hardening  iron  and  steel  in 
ovens.  Intensit  is  a  hardening  powder  for  hardening  iron  and 
steel  in  open  fires;  it  is  used  in  place  of  potassium  ferro- 
cyanide.  There  are  other  powders  of  a  similar  nature  with 
special  names  differing  only  in  the  proportion  of  active  in- 
gredients that  they  contain.  These  products  are  of  consider- 
able importance  to  metallurgy,  since  they  are  cheap,  yet 
efficient  for  the  purposes  for  which  they  are  sold. 


CHAPTER  II. 


Preparation  and  Properties  of  Cyanamide. 


PREPARATION. 

Free  cyanamide,  CN.NHg,  was  first  obtained  by  Bineau,  in 
1838,  by  the  action  of  ammonia  on  chlorcyan,  but  it  was  not 
isolated  by  him  from  the  ammonium  chloride  with  which  it 
was  formed.  The  Italian  chemists  Cloez  and  Cannizzaro,^  in 
1 85 1,  effected  the  separation,  and  gave  the  first  description  of 
the  compound. 

Their  method  consists  in  passing  chlorcyan  into  a  solution 
of  ammonia  in  absolute  ether,  filtering  off  the  crystalline  am- 
monium chloride  and  evaporating  the  solution  in  vacuo  below 
40°.  The  reaction  takes  place  according  to  the  following 
equation : 

2NH3  +  CNCl  «--  CNCl,  NH,  4-  NH. 

It  can  also  be  prepared  by  the  action  of  freshly  precipitated 
mercuric  oxide  on  thio-urea,  in  the  presence  of  a  little  am- 
monium thiocyanate,  which  dissolves  some  of  the  mercuric 
oxide  as  the  double  thiocyanate,  and  so  renders  it  more  active : 
NH,  NH, 

S:C/  "^  ^\         +  ^«^ 

NH,  N 

It  is  most  conveniently  prepared  from  either  commercial 
sodium  cyanamide  or  commercial  calcium  cyanamide. 

From  Commercial  Sodium  Cyanamide.^ — Twenty-five  grams 
of  the  salt  are  gradually  added  to  37  grams  of  hydrochloric 
acid  (sp.  gr.  1.19)  with  strong  cooling,  and  the  water  is  re- 
moved by  distillation  in  vacuo  below  40°  C.  The  residue 
solidifies  on  cooling;  it  is  extracted  with  ether,  the  ether  dis- 
tilled off   from  the  solution,   and   the  cyanamide  caused   to 

^  Compt.  rend.,  XXXII,  62.  A,  78,  229,  and  Leibig's  Annalen  78,  229. 

^  Caro,  Schiick,  Jacoby,  Zeit  Angew  Chem.  1910,  XXIII,  2405,  2417. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND   USES         II 

crystallize  by  cooling.  It  is  purified  by  recrystallization  from 
ether.     Yield  about  5  grams. 

From  Commercial  Calcium  Cyanamide. — Fresh  commercial 
Cyanamid  or  better,  the  unhydrated  lime-nitrogen,  is  extracted 
with  cold  water  (solubility  about  0.9  grams  nitrogen  in  100  cc. 
water).  The  calcium  is  removed  either  with  oxalic  acid  or 
aluminium  sulphate,  but  preferably  with  the  latter.  After  re- 
moval of  the  calcium  sulphate  and  alumina  by  filtration,  the 
filtrate  is  evaporated  in  vacuo  below  40°,  and  the  residue  ex- 
tracted with  ether.  It  can  be  purified  by  recrystallization  from 
ether. 

PROPERTIES  OF  CYANAMIDE. 

Cyanamide,^    CN.NHg,    most    probably    has    the    formula 

C  <^         ,  although  in  a  very  few  reactions  it  seems  to  act  as 

if  it  were  carbodiimide,  CZ        .     It  is  a  colorless,  crystal- 

line  solid,  which  melts  at  41-42°  C,  as  usually  prepared.  It 
can  be  undercooled  to  12°  without  solidifying.  On  stirring 
with  a  sharp-pointed  glass  rod  the  undercooled  liquid  freezes. 
The  carefully  purified  substance  melts  sharply  at  46°  C.^  It 
is  easily  soluble  in  water,  alcohol  and  ether,  and  is  volatile  in 
steam.  It  is  slightly  soluble  in  carbon  disulphide,  chloroform 
and  benzol. 

Action  of  Heat. — Pure  cyanamide  is  perfectly  stable  at  ordi- 
nary temperatures,  but  polymerizes  slowly  on  heating  above 
its  melting  point.  Impure  cyanamide  polymerizes  slowly  at 
ordinary  temperatures.     The  principal  polymer  is  dicyandia- 

mide,   NH  :  C<  >CN,  or  (H^CNJ,,  which  is  probably 

cyan-guanidine.      By  strong  heating,    other  derivatives   are 

^  Sidgwick,  Organic  Chemistry  of  Nitrogen,  p.  216,  (Oxford,  1910). 
2  G.  Henschel,  Diss.  Univ.  of  Leipzig,  191 2. 


12         CYANAMID — MANUFACTURE,    CHE:MISTRY    AND    USES 

formed,    the    most    important    of    which    are,    the    polymer 

N 

^\ 

Tricyantriamide  or  Melamine  H^N  —  C      C  —  NH2,  and  Me- 

I        11 
N      N 

^/ 
C 

I 

lam,  CgHjNjj,  and  Mellon,  C5H3N9.  Ammonia  is  evolved 
during  the  formation  of  these  bodies.  By  the  action  of  super- 
heated steam  the  conversion  of  cyanamide  to  ammonia  is 
almost  quantitative. 

Action  of  Acids.^ — Cyanamide  reacts  readily  with  acids ;  with 
nitric  acid  forming  urea  nitrate  (95  per  cent,  conversion) ; 
with  sulphuric  acid  and  phosphoric  acid  giving  mostly  urea, 
(about  95  per  cent,  conversion)  together  with  some  ammeline, 
CsNgCNHJpH;  ammelide,  C3N3(NH,)  (OH)^;  possibly 
cyanuric  acid,  C3N3(OH)3,  and  some  ammonia. 

Cyanamide  combines  directly  with  the  haloid  acids.  It  com- 
bines slowly  with  free  HgS,  readily  with  yellow  ammonium 
sulphide,  with  formation  of  thio-urea.  Thio-urea  is  also 
formed  by  the  action  of  thioacetic  acid  on  cyanamide  in 
alcoholic  solution.  Acetic  acid  produces  principally  ammo- 
nium acetate  (about  80  per  cent,  conversion)  and  some  urea. 

Action  of  Alkalies.=^— The  strong  alkalies  KOH  or  NaOH 
in  aqueous  solutions  produce  almost  entirely  urea,  with  no 
trace  of  dicyandiamide ;  weak  alkalies,  NH4OH  or  MgO,  pro- 
duce dicyandiamide  almost  exclusively  at  first,  and  then 
ammonia.    CaO,  however,  produces  a  mixture  of  urea,  dicyan- 

diamide,  ammeline,  amidodicyanic  acid  (  O  :  C<^  ) ,. 

^  ^NH  —  CN^ 

ammonia  and  other  bodies. 

^  Ulpiani,  Gas  Chim.,  Ital.  II,  No.  4,  358-417. 
'^  Beilstein's  Handbuch  der  Organische  Chemie. 


CYANAMID MANUI^ACTUR^,    CHE^MISTRY    AND    USKS         1 3 

Hence,  with  strong  acids  and  strong  bases,  cyanamide  in 
aqueous  solutions  forms  principally  urea;  with  weak  acids 
principally  ammonium  salts;  with  weak  bases  dicyandiamide, 
which  decomposes  further  to  ammonia;  with  lime,  a  mixture 
of  urea,  dicyandiamide  and  other  derivatives. 

Action  of  Oxidizing  and  Reducing  Agents. — In  the  chapter 
on  availability  it  will  be  shown  that  oxidizing  agents  convert 
the  nitrogen  of  cyanamide  or  its  derivatives  into  forms  more 
insoluble  in  water  and  less  easily  decomposed  by  strong 
alkalies. 

By  the  action  of  zinc  and  hydrochloric  acid,  cyanamide  yields 
ammonia  and  methylamine: 

CN.  NH,  +  H,  —  CNH  +  NH3, 
CNH  H-  2H,  —V  CH3  .NH,. 

On  heating  with  potassium  nitrite  solution  a  violent  reaction 
takes  place,  and  COo,  N2  and  dicyandiamide  are  produced : 
4CN.NH,  +  4KNO2 ^  2K,C03  +  4N2  +  (CN.NHJ,  +  2H,0. 

Other  Reactions.^ — In  cyanamide,  either  one  or  both  of  the 
hydrogen  atoms  can  be  displaced  by  metals,  alkyl  or  aryl 
groups,  or  by  alcohol  or  acid  radicals.  It  combines  with 
amino-acids,  especially  in  the  presence  of  ammonia.  It  com- 
bines with  ammonium  chloride  at  high  temperatures,  forming 
guanidine  hydrochloride.  Heated  with  ammonium  sulphide 
it  yields  guanidine  hydrosulphide.  It  combines  directly  with 
cyanogen  to  form  a  yellow,  amorphous  powder.  With  potas- 
sium cyanate  it  forms  potassium  amidodicyanate,  K.C2H2N3O. 
It  combines  directly  with  chloral,  and  also  with  aldehydes,  but 
with  the  separation  of  water. 

Metal  Salts. — The  dimetal  salts  of  the  alkali  metals  can  be 
prepared  only  in  the  dry  way,  since  in  aqueous  solution  they 
lose  one  of  the  metal  ions  by  hydrolysis.  Thus,  NasCNg  in 
aqueous  solution  yidds  NaHCNg: 

Na,CN,  +  H,0  =  NaHCN,  +  NaOH 
1  Beilstein,  Handbuch  der  Org.  Chem. 


14         CYANAMID manufacture:,    CH]E:MISTRY    AND    USEJS 

NagCN^  on  fusion  with  carbon  yields  sodium  cyanide: 
Na^CN,  +  C  —  2NaCN. 

/NCa 
Calcium  Cyanamide,  CaCN,  or  C^        ,  can  be  made  by  the 

fusion  of  calcium  cyanate:^ 

Ca  (CNO)^  — >  CaCN,  +  CO, 

or  by  fusion  of  cyanamide  or  its  polymers  with  calcium  oxide. 
Calcium  cyanamide  forms  colorless  crystals  which  sublime 
at  about  1,090°  C.  at  atmospheric  pressure.  It  is  insoluble  in 
alcohol,  but  easily  soluble  in  water  (about  2.5  g.  in  100  cc. 
water  at  25°  C).  Upon  solution  of  the  calcium  cyanamide  in 
water  it  is  directly  hydrolyzed  into  the  acid  calcium  cyanamide 
and  calcium  hydroxide. 

2CaCN2  +  2H,0  —  Ca(CN.NH)2  +  Ca(OH),. 

That  such  hydrolysis  takes  place  as  indicated  by  the  equa- 
tion is  shown  by  the  relative  amounts  of  lime  and  nitrogen 
existing  in  solutions  of  calcium  cyanamide.  C.  Ulpiani^  inves- 
tigated the  relation  of  lime  to  nitrogen  in  a  solution  of  calcium 
cyanamide  kept  at  a  constant  temperature  for  several  weeks. 
At  intervals  of  several  days  determinations  were  made  of 
total  nitrogen,  nitrogen  in  the  form  of  cyanamide,  and  calcium 
in  solution.  It  was  noted  that  crystals  of  pure  calcium 
hydroxide,  as  determined  by  analysis,  were  deposited  on  the 
walls  of  the  vessel  after  a  day  or  two.  The  quantities  of 
lime  and  nitrogen  found  in  the  solution  are  shown  in  Fig.  i. 

Since  the  solubility  of  calcium  cyanamide  is  much  greater 
than  that  of  calcium  hydroxide,  a  concentrated  solution  of 
calcium  cyanamide  is,  after  hydrolysis,  saturated  with  respect 
to  calcium  hydroxide.  In  addition,  there  is  present  lime  as 
a  calcium  compound  of  cyanamide.  If  this  compound  is  cal- 
cium acid  cyanamide,  Ca(CN.NH)2,  there  will  be  in  solution 
one  atom  of  calcium  to  four  of  nitrogen,  or  56  parts  by  weight 

^  Beilstein  loc  cit. 

'  Rend.  Soc.  Chim.  di  Roma,  n.  4  (1906). 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 


15 


of  CaO  to  56  of  N,  or  equal  weights  of  each.  By  reference 
to  the  curves  in  Fig.  i  it  is  seen  that  if  the  ordinate  represent- 
ing the  amount  of  CaO  present  as  Ca(OH)2  is  subtracted 
from  the  ordinate  of  total  CaO,  the  ordinate  of  CaO  combined 
in  other  forms  (with  cyanamide)  would  coincide  with  the 
ordinate  of  nitrogen  present  as  cyanamide ;  that  is,  the  amounts 
of  CaO  and  N  present  are  in  the  relation  demanded  by  the 
formula  CaCCN.NH),. 

On  long  standing  of  the  solution,  the  acid  salt  Ca(CN.NH)2 
decomposes,   forming  principally  urea,   some   dicyandiamide. 


H-Total^ - 
0a0-7ota] 

D-  as 
Cyanamide  ■'^^ 


Fig.  I.— Variation  of  nitrogen  and  calcium  in  a  solution  of  lime-nitrogen. 

and  small  quantities  of  melamine,  amidodicyanic  acid  and 
ammonia.  The  dicyandiamide  diminishes  slowly,  and  finally 
probably  disappears  entirely.  This  is  shown  in  the  following 
analyses  by  G.  Liberi^  of  a  solution  made  by  extracting  lime- 
nitrogen  containing  ^8.63  per  cent,  cyanamide  nitrogen,  with 
twenty  times  its  weight  of  cold  water.  The  nitrogen  figures 
are  given  as  a  percentage  of  the  dry  lime-nitrogen. 

1  Ann.  R.  Staz.  Chim.  Agrar.  Sper  di  Roma.,  191 1,  Vol.  V,  Series  II. 


l6         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

Nitrogen  in  solution 

As  cyanamide  As  dicyanamide 

After  Per  cent.  Per  cent. 

I  day 14.56  0,70 

3  days 11.76  1.54 

6  days 9.10  2.84 

II  days 5.18  2.24 

18  days > 1.75  1. 71 

31  days 0.00  1.25 

45  days 0.00  0.84 

58  days 0.00  0.53 

76  days 0.00  0.23 

Basic  calcium  cyanamide  is  formed  in  solutions  containing 
an  excess  of  lime: 

N  N 

///  /// 

Cv  +  Ca(OH),  ^    Cv        /CaOH 

\NCa  \N< 

\CaOH 

It  can  be  obtained  from  lime-nitrogen  by  extracting  with  a 
small  portion  of  water,  filtering,  and  allowing  the  solution  to 
stand  several  hours.  Long,  needle-shaped  white  to  trans- 
parent crystals  separate  out  on  the  walls  of  the  vessel.  Filter 
with  suction  in  the  absence  of  carbon  dioxide  (under  a  bell- 
jar).     Dry  under  a  bell-jar  over  caustic  potash. 

This  salt  is  almost  insoluble  in  water.  In  the  dry  condition 
it  is  stable  at  ordinary  temperatures,  but  when  heated  to 
120°  C.  it  rapidly  decomposes  to  dicyandiamide  and  calcium 
hydroxide. 

Calcium  cyanamide  carbonate^  is  readily  formed  by  the 
action  of  carbon  dioxide  on  calcium  cyanamide  in  the  presence 
of  moisture.  It  can  be  prepared  by  extracting  lime-nitrogen 
with  one  and  one-half  times  its  weight  of  water,  filtering  and 
bubbling  CO2  through  the  filtrate.  In  about  half  an  hour  a 
white  precipitate  forms,  which  can  be  filtered  and  washed  with 
alcohol  or  ether. 
^  Ulpiani,  loc  cit. 


CYANAMID — MANUFACTURE),    CHEMISTRY    AND    USES         1 7 

N 

/// 
CaCN,  +  CO2  -f  H,0  —  Cv        /Ca 

\N<(    I    5H,0. 

Calcium  cyanamide  carbonate  is  somewhat  insoluble  in  water, 
and  insoluble  in  alcohol  and  ether.  On  standing  in  dry  air 
it  slowly  loses  4  molecules  of  water  of  crystallization,  and  at 
the  same  time  decomposes  to  dicyandiamide  and  calcium  car- 
bonate.   The  same  change  takes  place  rapidly  when  heated : 

N 

/// 
2C\       /Ca.5H,0  •--  (CN.NH,),  +  2CaC03  +  8H,0 
\N<    I 

Silver  Cyanamide,  CN.NAg2. — Obtained  on  treating  an 
ammoniacal  solution  containing  cyanamide  with  very  dilute 
(i:  150)  solution  of  silver  nitrate.^  More  concentrated  solu- 
tions yield  a  mixture  of  this  salt  and  double  or  basic  silver 
salts,  containing,  however,  all  the  cyanamide. 

Silver  cyanamide  is  an  amorphous,  yellow  substance,  almost 
insoluble  in  dilute  ammonia  or  caustic  potash  at  ordinary  tem- 
peratures, soluble  in  hot  ammonia  solutions,  easily  soluble  in 
dilute  nitric  acid.  It  is  easily  soluble  in  alkali  cyanide  solution, 
but  if  an  excess  of  silver  nitrate  is  added,  a  white,  crystalline 
double  salt  of  silver  cyanide  and  silver  cyanamide  is  precipi- 
tated. 

When  potassium  hydroxide  is  added  to  a  cyanamide  solution 
containing  silver  nitrate  in  excess  an  insoluble  mixed  precipi- 
tate of  silver  cyanamide  and  brown  silver  oxide  is  formed, 
which  contains  all  the  cyanamide  nitrogen. 


y 


NH, 


Dicyandiamide,'  NH  :  C<^  .—Obtained   by   extract- 

\NH.CN 

ing  lime-nitrogen  with  boiling  water,  concentrating  the  solu- 

^  Caro,  Schiick,  Jacoby,  loc  cit. 
2  Beilstein,  loc  cit. 


l8         CYANAMID — MANUFACTURE^    CHE:MISTRY    AND    USES 

tion  to  a  syrup  and  allowing  to  crystallize.  It  forms  trimetric 
plates  or  thin  leaves,  melting  at  205°  C.  It  is  decomposed  by 
heating,  with  evolution  of  ammonia  and  formation  of  mela- 
mine,  melam,  and  other  derivatives.  Dicyandiamide  is  some- 
what easily  soluble  in  water  and  alcohol,  but  almost  insoluble 
in  ether.  It  combines  with  ammonium  chloride  at  150°,  giving 
diguanide  hydrochloride,  C2H7N5HCI;  with  HCl  at  150°  gives 
guanidine  hydrochloride,  CH5N3HCI;  on  boiling  with  baryta 
it  gives  amidodicyanic  acid  and  ammonia;  with  zinc  and  HCl 
yields  methylamine  and  ammonia;  with  H^S  it  gives  guanyl- 
thiourea;  on  heating  with  urea  or  cyanuric  acid  it  forms 
ammelin,  C3H5N5O,  and  ammonia. 

Treated  with  weak  or  strong  acids,  or  with  strong 
alkalies,      dicyandiamide     goes     over     to     dicyandiamidine, 

NH  :  C^  ,    caustic  crystals,    easily    soluble    in 

^NH.CO.NH, 

water  and  alcohol. 

Dicyandiamide,  treated  with  silver  nitrate  solution,  forms 
additional  compounds  containing,  according  to  the  conditions, 
one,  two  and  three  molecules  respectively,  of  dicyandiamide 
per  molecule  of  silver  nitrate.  Cold  caustic  potash  added  to 
a  dicyandiamide  solution  containing  sufficient  silver  nitrate 
causes  a  white  to  brown  mixture  of  precipitates  of  silver 
dicyandiamide  and  silver  oxide.  Silver  dicyandiamide  is 
slightly  soluble  in  water,  easily  soluble  in  ammonia,  soluble  in 
hot  nitric  acid;  on  prolonged  boiling  with  caustic  potash  is 
converted  into  silver  cyanamide,  CN.NAgg,  and  cyanamide, 
which  polymerizes  again  to  dicyandiamide. 

If  silver  nitrate,  then  nitric  acid,  is  added  to  a  solution  of 
dicyandiamide,  a  white  precipitate  is  formed,  insoluble  in 
cold,  soluble  in  hot  nitric  acid  or  in  excess  of  ammonia.  (Iden- 
tification in  mixtures  of  cyanamide  and  dicyandiamide.  Cyan- 
amide, it  will  be  remembered,  gives  a  yellow  precipitate  with 
dilute  silver  nitrate,  soluble  in  nitric  acid,  but  insoluble  in 
ammonia.) 


CHAPTER  III. 


Analytical  Methods. 


DETERMINATION  OF  TOTAL  NITROGEN  IN  CYANAMID. 

Practically  all  the  Cyanamid  manufactured  in  this  country 
prior  to  January  i,  1912,  contained  about  23  per  cent,  of  its 
total  nitrogen  in  the  form  of  nitrates.  Hence,  for  the  deter- 
mination of  total  nitrogen  in  such  Cyanamid  it  is  necessary  to 
use  a  method  that  will  determine  nitrate  nitrogen  as  well  as 
nitrogen  derived  from  Cyanamid.  For  this  purpose  the  Official 
Gunning  method,  modified  for  nitrates,  is  suitable.  The 
period  of  digestion  should  be  at  least  five  hours.  The  influ- 
ence of  the  period  of  digestion  is  shown  in  the  following  values 
obtained  on  a  sample  of  Cyanamid  containing  nitrates: 

Per  cent,  nitrogen 

2  hours   digestion 15.61 

3  "  "  15.76 

4  "  "  16.03 

5  *'  "  16.06 

All  the  Cyanamid  manufactured  in  this  country  since  Jan- 
uary I,  1912,  is  free  of  nitrates,  and  therefore,  the  simple 
Kjeldahl  or  Gunning  method  may  be  used.  The  Gunning, 
which  is  in  general  use,  is  carried  out  as  follows : 

REAGENTS  REaUIRED. 

N/2  (Half-normal)  Sulphuric  or  hydrochloric  acid. 

N/io    (Tenth-normal)    Sodium   hydroxide,   or   ammonium 

hydroxide. 
Sulphuric  acid,  C.  P.,  specific  gravity  1.84. 
Sodium  hydroxide,  saturated  solution. 
Potassium  sulphate,  C.  P. 
Cochineal  indicator. 

To  determine  nitrogen  weigh  out  0.7  gram  of  finely  ground 
sample.     Each  cc.  of  half-normal  acid  is  equivalent  to  i  per 


20         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

cent,  nitrogen.  To  determine  ammonia  weigh  out  0.85  gram 
of  finely  ground  sample.  Each  cc.  of  half-normal  acid  is 
equivalent  to  i  per  cent,  ammonia. 

Procedure. — Place  the  carefully  weighed  sample  in  a  Kjeldahl 
flask  of  about  300  cc.  capacity.  Add  10  grams  of  ground 
potassium  sulphate.  Shake  until  well  mixed  with  the  sample. 
Add  25  to  30  cc.  of  concentrated  sulphuric  acid  and  shake 
until  well  mixed.  Heat  slowly  for  30  minutes,  then  heat  with 
a  full  flame  for  one  and  one-half  hours.  Cool,  dilute,  and 
transfer  to  a  distillation  flask.  (Distillation  can  be  made  from 
the  digestion  flask  if  desired.)  Add  an  excess  of  sodium 
hydroxide,  and  distil  200  cc.  into  a  measured  quantity  of  the 
standard  half-normal  acid,  containing  some  cochineal  indi- 
cator.   Titrate  the  excess  of  acid  with  tenth-normal  alkali. 

DETERMINATION  OF  CYANAMIDE  AND 
DICYANDIAMIDE. 

Caro  Method. — Of  the  various  methods  for  determining 
cyanamide  and  dicyandiamide,  that  of  Caro^  seems  to  be  the 
best.    The  reagents  used  are  as  follows : 

(a)  Silver  acetate  solution.  100  grams  of  silver  acetate  are 
placed  in  a  liter  flask,  covered  with  400  cc.  of  10  per  cent, 
ammonium  hydroxide,  and  the  flask  is  filled  to  the  mark  with 
water. 

(b)  10  per  cent,  solution  of  potassium  hydroxide. 

The  procedure  is  as  follows:  5  g.  of  Cyanamid  or  lime- 
nitrogen  is  agitated  by  hand  or  in  a  shaking  machine  with 
450  cc.  of  water  for  about  2j4  hours,  and  the  flask  filled  to 
500  cc.  An  aliquot  part  (250  cc.)  is  treated  with  ammonia 
until  it  smells  strongly  thereof  and  then  with  silver  acetate 
solution  in  excess.  The  precipitate  of  silver  cyanamide  salts 
(p.  12),  after  shaking  and  standing  a  little  while,  is  gathered 
on  a  nitrogen-free  filter,  washed  with  water  until  no  ammo- 
nium salts  run  through,  and  the  nitrogen  in  it  is  determined 
by  the  Kjeldahl  method. 

^  Caro,  Schiick,  Jacoby— loc  cit. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         21 

An  aliquot  part  of  the  filtrate,  now  free  from  cyanamide, 
is  treated  with  potassium  hydroxide  solution  in  excess,  and  is 
boiled  until  no  more  ammonia  comes  off.  The  precipitate  con- 
tains all  the  dicyandiamide  and  some  silver  oxide.  Dilute  the 
solution  with  an  equal  volume  of  water,  filter  on  a  nitrogen- 
free  filter,  wash  with  some  water,  and  determine  nitrogen  in 
the  precipitate  by  the  Kjeldahl  method. 

Brioux^  claims  that  the  boiling  of  the  strongly  alkaline 
cyanamide-free  solution  containing  the  precipitate  of  silver 
dicyandiamide  and  silver  oxide  causes  a  conversion  of  about 
1.5  per  cent,  of  the  total  nitrogen  of  the  dicyandiamide,  and  he 
has  modified  the  method  so  as  to  obviate  this  error.  His 
method  is  briefly  as  follows : 

Brioux's  Modified  Caro  Method. — Extract  the  soluble  nitro- 
gen from  I  or  2  grams  of  finely  ground  sample  by  frequent 
shaking  for  three  or  four  hours  in  a  flask  with  250  cc.  cold 
water,  and  filter  through  a  dry  filter  without  washing.  In 
one  aliquot  portion  of  100  cc.  of  the  filtrate  determine  cyana- 
mide and  dicyandiamide,  and  in  the  other  determine  cyanamide 
alone. 

For  combined  cyanamide  and  dicyandiamide  nitrogen :  For 
each  0.1  gram  nitrogen  (approx.)  in  the  solution  add  20  cc. 
of  5  per  cent,  silver  nitrate  solution.  Then  add  20  cc.  of 
10  per  cent,  potassium  hydroxide  solution.  A  brown  precipi- 
tate of  mixed  cyanamide  and  dicyandiamide  salts  forms. 
Filter  and  wash  with  cold  distiled  water.  Determine  total 
nitrogen  in  the  residue  by  the  Kjeldahl  process,  substituting 
I  gram  copper  sulphate  in  place  of  the  mercury. 

For  cyanamide  nitrogen :  In  the  other  portion  of  the  extract 
from  the  sample  add  for  each  o.i  gram  nitrogen,  20  cc.  of 
5  per  cent,  silver  nitrate  solution.  Add  an  excess  of  ammonia. 
A  yellowish-brown  precipitate  forms.  Filter  and  wash  with 
water  slightly  ammoniacal,  finishing  with  cold  distilled  water 
until  the  washings  are  free  from  soluble  silver  salts.  Dissolve 
the  residue  in  dilute  nitric  acid  (1:2)  and  determine  silver 
^  Annales  de  la  Science  agron.  francaise  et  etrangere,  April  1910. 


22         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

by  the  sulphocyanate  or  other  convenient  method.     One  atom 
of  silver  corresponds  to  one  atom  of  nitrogen. 

In  both  the  Caro  and  Brioux  methods,  however,  from  25  to 
30  per  cent,  of  the  urea  present  is  precipitated  in  caustic  potash 
solution  as  silver  salts  along  with  the  dicyandiamide.^  Since 
Cyanamid  frequently  contains  more  urea  than  dicyandiamide 
this  occasions  considerable  error.  Henschel^  found  that  by  the 
Caro  method  about  7  per  cent,  of  the  nitrogen  as  dicyandiamide 
was  converted  to  other  forms,  presumably  by  the  action  of  the 
hot  caustic  alkali  in  boiling  off  the  the  ammonia.  The  total 
nitrogen  was  not  diminished,  hence  the  urea  (?)  nitrogen  was 
increased  at  the  expense  of  the  dicyandiamide. 

Determination  of  Urea. — Caro  determines  the  total  nitrogen 
remaining  in  the  filtrate  from  the  dicyandiamide  separation  and 
designates  it  as  urea.  Since,  however,  some  of  the  urea  is 
precipitated  along  with  the  dicyandiamide  and  since  the  filtrate 
may  also  contain  other  derivatives,  the  method  can  hardly  be 
considered  as  satisfactory.  Caro  also  recommends  Liebig's 
titration  method  for  the  determination  of  the  urea  in  the 
filtrate.  Ulpiani,^  however,  claims  that  the  mercuric  nitrate 
used  for  the  precipitation  of  urea  in  this  method,  also  pre- 
cipitates cyanamide  and  dicyandiamide,  if  present,  dicyandia- 
midine,  amidodicyanic  acid,  ammonia,  ammonium  salts,  and 
probably  all  nitrogen  compounds  found  in  lime-nitrogen. 
Ulpiani  suggests  the  direct  solution  of  the  sample  of  lime- 
nitrogen  or  Cyanamid  with  alcohol,  but  since  dicyandiamide  as 
well  as  urea  is  soluble  in  alcohol,  this  procedure  would  not 
simplify  the  problem  very  much. 

The  question  of  analysis  of  cyanamide  derivatives  is  much 
in  need  of  scientific  study,  but  for  the  present  it  will  be 
sufiicient  for  most  purposes  to  determine  total  nitrogen  in  a 
given  sample  of  Cyanamid,  then  to  determine  cyanamide  and 

^  Brioux,  loc.  cit. 

'  Georg  Henschel,  Das  Verbal  ten  des  technischen  Calciumcyanamides 

bei  der  Aufbewabrung  sowie  unter  dem  Einfluss  von  Kulturboden 

und  KoUoiden — Diss.  Univ.  Leipzig.  191 2. 
^  Ulpiani,  loc.  cit. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         23 

dicyandiamide  by  the  Caro  method,  and  to  consider  the  differ- 
ence as  being  equivalent  to  the  original  urea.  The  other 
derivatives  usually  occur  in  such  small  quantities  that  they  are 
practically  negligible. 

IDENTIFICATION  OF  AMIDODICYANIC  ACID. 

The  following  is  based  upon  the  procedure  given  by  Ulpiani^ 
for  the  identification  of  amidodicyanic  acid. 

Remove  the  cyanamide  and  dicyandiamide  (Brioux's 
method),  carefully  neutralize  the  filtrate  v^ith  sulphuric  acid, 
and  treat  with  copper  sulphate.  In  a  day  or  two  greenish 
crystals  of  copper  amidodicyanate  separate  out.  Sometimes 
there  is  also  a  slight  precipitate  of  copper  salts  of  cyanamide 
and  dicyandiamide,  which  are  easily  washed  out  by  rapid  de- 
cantation,  since  the  copper  amidodicyanate  is  much  heavier.  The 
copper  amidodicyanate  has  the  formula  Cu(C2H2N30)2 .4H2O. 
It  is  further  identified  by  mixing  the  copper  salt  with  ammonia 
and  treating  the  solution  with  hydrogen  sulphide.  The  copper 
sulphide  is  filtered  off,  and  the  filtrate  concentrated,  when  a 
white  precipitate  of  thiobiuret  is  formed.  This  loses  water  at 
100°  and  melts  at  185°.  With  copper  sulphate  a  solution  of 
thiobiuret  gives  a  white  precipitate. 

IDENTIFICATION  OF  AMMELINE. 

Ulpiani^  claims  that  ammeline  can  be  detected  in  old  lime- 
nitrogen  as  follows : 

Extract  the  sample  with  dilute  nitric  acid.  Filter  and  just 
neutralize  the  filtrate  with  ammonia.  A  white  precipitate  of 
ammeline  is  obtained,  insoluble  in  water,  soluble  in  alkalies  or 
mineral  acids.  Analysis  should  show  the  solid  to  have  the 
formula  C3H.5N5O. 

1  Gaz  Chim.  Ital  1908,41  No.  4,  358-417. 
^  loc.  cit. 


CHAPTER  IV. 


Storage  of  Cyanamid. 


On  exposure  to  the  atmosphere,  Cyanamid  absorbs  moisture 
and  carbon  dioxide.  This  absorption  of  foreign  material,  of 
course,  increases  the  weight  of  the  exposed  sample,  and  hence 
decreases  the  percentage  of  the  original  constituents.  Neglect 
to  observe  this  increase  in  weight  and  corresponding  decrease 
of  percentages  led  some  early  investigators  to  declare  that  nitro- 
gen is  lost  when  Cyanamid  is  stored  for  any  great  length  of 
time.  It  has  lately  been  shown  by  carefully  conducted  experi- 
ments in  the  laboratory  as  well  as  on  a  large  scale,  that  under 
conditions  of  storage  customary  for  fertilizer  materials  there  is 
no  loss  of  nitrogen. 

Factory  Test. — When  Cyanamid  is  stored  in  ordinary  burlap 
bags  only  the  exposed  surfaces  can  receive  moisture  and  carbon 
dioxide,  and  penetration  into  the  interior  of  the  bag  or  pile  is 
necessarily  difficult.  Even  in  damp  climates,  such  absorption 
is  not  very  large  when  considered  in  its  relation  to  the  entire 
pile.  Thus,  a  pile  of  Cyanamid  weighing  94,083  pounds,  and 
analysing  15.63  per  cent,  nitrogen  was  stored  in  a  warehouse 
over  and  a  few  feet  above  the  surface  of  the  St.  Johns  river  at 
Jacksonville,  Florida,  from  July  7th  to  January  13th,  and  was 
then  carefully  weighed  and  sampled  by  the  purchaser,  the 
sample  being  taken  from  different  portions  of  two  out  ot  every 
three  bags  in  the  lot. 

Weight 

Original 94.083 

After  7  months-   101,506 

Hence,  even  in  this  damp  climate,  where  rains  occur  almost 
daily  during  the  summer  months,  the  rate  of  increase  of  weight 
is  a  little  more  than  one  per  cent,  a  month,  while  the  nitrogen 
content  remains  constant. 


Per  cent,  increase 
in  weight.  7  mo's 

Analysis 
nitrogen 

Pounds 
nitrogen 

.... 

15.63 

14,705 

7.9 

14.52 

14,740 

CYANAMID — manufacture;,    CHEMISTRY    AND    USES 


25 


Test  of  Two  Bags. — A  test  on  a  smaller  scale  was  made  by 
the  author,  at  Niagara  Falls,  Ontario,  in  1912.  Two  ordinary 
burlap  bags,  each  holding  about  150  pounds  of  Cyanamid 
hydrated  on  November  12,  191 1,  were  exposed  November  17, 
191 1,  on  a  raised  platform  made  of  4-inch  strips  spaced  4  inches 
apart.  The  room  was  dry,  well-ventilated  by  an  open  window, 
and  kept  most  of  the  time  between  10°  and  35°  C.  Samples 
were  drawn  and  the  weight  of  the  bags  was  taken  just  before 
they  were  laid  out  on  the  platform.  At  the  end  of  each  period 
of  exposure  as  noted  below,  the  bags  were  carefully  weighed, 
and  the  contents  were  removed.  After  thorough  mixing  of 
the  material  a  sample  was  drawn,  and  the  bags  were  refilled, 
tied,  weighed,  and  again  laid  out  on  the  platform  for  further 
exposure.     The  following  data  were  obtained: 


Moisture 
Per 
Sample  drawn  cent. 

Nov.  17,  1911 0.00 

Dec.  17,  1911 0.40 

Jan.  17,  1912 0.47 

Feb.  17,  1912 0.46 

May  17,  1912 0.67 


r  A.— Anai^yses. 

Carbon 

dioxide 

Per 

cent. 

Nitrogen 
Per 
cent. 

Calcium 
Per 
cent. 

-tioi 

1.75 

16.54 

40.34 

0.4100 

2.12 

16. 1 1 

39-94 

0.4095 

2.75 

16.II 

39-34 

0.4095 

2.87 

15.96 

38-94 

0.4099 

4.05 

15-69 

37-94 

0.4136 

Weights. 

Per  cent, 
gain  in 

weight  Per  cent.  Per  cent. 

Weight    Gain  in        since  nitrogen  Per  cent,    nitrogen 

pounds    weight      previous  calcu-  nitrogen       gained 

Date                        net       pounds    weighing  lated  found         or  lost 

Nov.  17,  1911 148.25        —  —  —  16.54  — 

Dec.  17,  1911 ^150.75      2.50        1.69        16.266        16.31        -fo«04 

"   "    "  ^149.25 

Jan.  17,  1912 150.50   1.25   0.84    16.131    16.11    —0.02 

"  "   ••  149.50 

Feb.  17,1912 150.50      i.oo        0.67        17.024        15.96        — 0.06 

"     *'       "    i5ofbo 

May  17,  1912 153.25      3-25        2.17         15-683         15.69        -f-o.oi 

^  Before  sampling. 
^  After  sampling. 


26         CYANAMID — MANUFACTURE:,    CHE:MISTRY    AND    USES 


Bag  B.~Anai.ysis. 

Carbon 

Moisture       dioxide  Nitrogen  Calcium 

Per                Per  Per                   Per               Ratio-^ 

Sample  drawn                   cent.             cent.  cent,                 cent.                        Ca 

Nov.  17,  191 1 0.00  1.75  16.34  40.53  0.4031 

Dec.  17,  191 1 0.43  2.10  16.09  39-94  0.4029 

Jan.  17,  1912 0.44  2.70  15.87  39.35  0.4033 

Feb.  17,  1912 0.46  2.83  15.70  38.94  0.4031 

May  17,  1912 0.69  3.96  15.50  38.76  0.3999 

Weights. 

Per  cent, 
gain  in 

weight     Per  cent.  Per  cent. 

Weight    Gain  in         since        nitrogen  Per  cent,    nitrogen 

pounds    weight       previous       calcu-  nitrogen      gained 

net        pounds      weighing       lated  found         or  lost 

Nov.   17,  1911 149.00         _  _  _  16.34  — 

Dec.  17,  1911 ^151.75       2.75         1.84         16.046        16.09         -fo.04 

"      "        "      '150.75 

Jan.  17,  1912 152.25       1.50        0.99         15.890         15.87         —0.02 

"     "       "     151.25 

Feb.   17,  1912 151-75      0.50        0.33         15.838         15.70        —0.14 

"     "       "     151.25 

May  17,  191 2 154.75       3-50         2.31         15-480         15.50         +0.02 

The  addition  of  free  moisture,  chemically  combined  moisture, 
and  carbon  dioxide  necessarily  increases  the  weight  of  the 
sample,  and  hence  causes  a  proportionate  decrease  in  the 
percentages  of  other  constituents.  It  is  evident  that  calcium 
cannot  escape  from  the  stored  material  either  by  volatilization, 
since  calcium  compounds  require  at  least  a  red  heat  before 
they  vaporize  appreciably,  or  by  leaching,  since  the  mass  re- 
mains practically  dry  for  years.  The  decrease  in  calcium  per- 
centage must  therefore  be  due  solely  to  the  addition  of  other 
matter,  and  the  ratio  of  the  calcium  percentages  before  and 
after  exposure  is  equal  to  the  inverse  ratio  of  the  weights  be- 
fore  and    after   exposure.     Thus    in   bag   A   the   ratios   are 

40.-^4       106.32        .,         ,       1  .  r  ^ 

- — ^^  = or  there  has  been  an  increase  01  6.32  per  cent. 

37.94       100.00 

on  the  original  weight.     As  shown  by  the  weighings,  the  in- 

^  Before  sampling. 
2  After  sampling. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         2/ 

crease  of  weight  was  5.46  per  cent,  of  the  original  weight.  The 
failure  of  the  two  results  to  check  more  closely  is  due  to  the 
difficulty  of  making  accurate  calcium  determinations  in 
Cyanamid. 

Since  the  absolute  quantity  of  calcium  remains  constant  in 
the  mass  exposed,  it  follows  that  if  the  absolute  quantity  of 
nitrogen  present  do  not  vary,  the  ratio  of  nitrogen  to  calcium 
must  remain  constant.  Inspection  of  the  data  obtained  as 
described  above  shows  that  this  is  actually  the  case  within 
sampling  and  analytical  limits  of  error.  Recapitulating  the 
results  by  analysis  and  by  the  weights  we  have : 

Increase  in  weight  Variation  of  nitrogen 

By  Ca  ratios      by  weighing  By  N/Ca  ratio  By  weighing 

Bag  A 6.32  5.46  +0-I4  +0.01 

Bag  B....  4.77  5,57  -o.io  -fo.o2 

Average  ..  5.54  5.51  +0.02  -f-o-oiS 

There  has  therefore  been  no  loss  of  nitrogen  under  ordinary 
factory  conditions  of  storage,  even  in  the  case  of  a  single 
exposed  bag,  which  exposes  a  relatively  larger  surface  per 
pound  of  material  than  a  large  pile  would  expose. 

Of  the  5.5  per  cent,  increase  in  weight,  approximately  0.7 
per  cent,  is  due  to  the  addition  of  free  moisture,  2.5  per  cent, 
to  addition  of  carbon  dioxide,  and  2.3  per  cent,  to  addition  of 
combined  water;  or,  of  the  total  increase  in  weight,  about  13 
per  cent,  is  due  to  free  moisture,  45  per  cent,  to  carbon  dioxide, 
and  42  per  cent,  to  chemically  combined  water. 

In  the  analyses  given  above,  free  moisture  was  determined 
by  the  decrease  in  weight  of  a  sample  heated  5  hours  at  100° 
C,  in  a  drying  oven  free  of  carbon  dioxide.  The  "combined" 
water  is,  properly  speaking,  not  present  as  water  at  all,  but 
represents  water  which  has  acted  hydrolytically  upon  calcium 
cyanamide  with  the  production  of  various  organic  derivatives. 
Such  hydrolyses  are  in  the  main  irreversible  by  drying.  The 
increase  in  weight  suffered  by  a  sample  of  Cyanamid  during 
storage  cannot,  therefore,  be  determined  by  simply  correcting 
final  analyses  to  the  so-called  "dry  basis,"  since  such  a  correc- 


28        €YANAMID MANUFACTURE),    CHEMISTRY    AND    USES 

tion  is  only  a  small  portion  of  the  true  correction  required.  The 
true  increase  in  weight  is  best  determined  by  direct  weighing 
of  the  initial  and  final  sample,  or  by  comparing  the  calcium 
content  of  the  initial  and  final  samples.  The  latter  involves 
very  accurate  calcium  determinations,  if  the  results  are  to  be 
significant. 

The  absorption  of  "combined  water"  and  of  carbon  dioxide 
takes  place  for  the  most  part  in  accordance  with  the  follow- 
ing equations,  which  probably  account  for  the  formation  of 
dicyandiamide,  urea,  calcium  cyanamide  carbonate,  and  cal- 
cium carbonate: 

2CaCN,  +  2H,0  =  Ca(CN.NH),  +  Ca(OH),, 
Ca(CN.NH),  +  2H,0  =  (H,CN,),  +  Ca(OH)„ 
CaCN,  H-  3H,0  =-  CO(NH,),  +  Ca(OH)„ 
CaCN,  4-  CO,  +  H,0  =  CaCN,.CO,.H,0, 
Ca(OH),  +  CO,  =  CaCO^  +  H,0. 

After  long  periods  of  exposure  there  are  formed  slight 
amounts  of  secondary  derivatives,  so  that  old  Cyanamid  will 
contain  the  following  substances : 

Calcium  cyanamide CaCN, 

Acid  calcium  cyanamid Ca(HCN2)2 

Basic  calcium  cyanamid CaCN2.Ca(OH)2 

Calcium  cyanamide  carbonate CaCN2C02.H20 

Dicyandiamide (H2CN2)2 

Urea CO(NH2)2 

Amidodicyanic  acid H3C2N3O  (slight  amounts) 

Melamine (H2CNj)3  (slight  amounts) 

Ammeline • H5C3N5O  (slight  amounts) 

Ammonium  hydroxide NH^OH  (traces) 

The  following  scheme  shows  the  relation  of  some  of  these 
forms  to  each  other,  and  a  possible  mechanism  for  their  deriva- 
tion from  calcium  cyanamide: 


CYANAMID — manufacture:,    CHEMISTRY    AND    USES         29 


xNCa 

/NH, 

2H,0 

Ca(OH), 

Calcium 
cyanamide. 

Cyan- 
amide. 

C^_       +  2H,0  «—  OC/           H-  2H,0  - 

NH. 

-i  ■ 

Cyanamide. 

Urea. 

Ammonium 
carbonate. 

C=NH 

c=o 

\ 

+    H,0 

+        NH,. 

Dicyandiamide. 

Amidodicyanic 
acid. 

C=NH 

C=NH 

\nh 

C=:NH 

+  H,0 

C=0 

+      NH,. 

\ 

.  >" 

c4 

^N 

■^N 

Mel 

amine. 

Ammeline. 

Relative  Amounts  of  Decomposition  Products. — The  relative 
amounts  of  these  decomposition  products  has  been  studied  in 
only  a  few  cases,  since  the  total  amounts  become  appreciable 
only  under  extraordinarily  severe  conditions  of  moisture.  A 
test  of  this  kind  is  reported  by  Brioux.^ 

^  Annales  de  la  Science  agronomique  francaise  et  etrangere,  April, 
1910. 


30         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

A  sample  of  lime-nitrogen  was  exposed  on  a  watch-glass 
in  a  bell- jar,  the  atmosphere  of  which  was  kept  saturated  with 
moisture  by  a  beaker  of  water  alongside  the  watch-glass.  The 
lo  gram  sample  after  8  months  exposure  weighed  18.75  grams. 
The  analyses  before  and  after  exposure  are  as  follows,  the 
third  column  showing  the  results  corrected  to  allow  for  in- 
crease in  weight. 

After 
Before        After       exposure 
exposure  exposure    corrected 

Total  nitrogen 17.08  8.99  16.84 

Insoluble  nitrogen 1.30  0.38  0.71 

Soluble  nitrogen  in  form  of  Cyanamid 15-05  0.14  0.26 

Soluble  nitrogen  in  form  of  Dicyandiamid 0.25  6.87  12.87 

Soluble  nitrogen  in  "other  forms  "   0.48  1.60  3.00 

The  loss  of  nitrogen,  in  the  form  of  free  ammonia,  has 
apparently  been  0.24  per  cent.  The  soluble  nitrogen  in  "other 
forms"  consists  principally  of  urea,  with  a  small  amount  of 
amidodicyanic  acid  and  ammeline. 

The  above  test  is  unusually  severe,  and  has  little  bearing 
upon  the  question  of  the  storing  qualities  of  Cyanamid.  Under 
similar  circumstances  it  takes  less  than  a  week  for  sodium 
nitrate,  ammonium  sulphate  and  calcium  nitrate  to  entirely 
dissolve  in  the  moisture  they  absorb,  while  basic  calcium 
nitrate  becomes  pasty  and  sticky  in  the  same  time.  The 
Cyanamid,  on  the  other  hand,  is  still  in  good  mechanical  con- 
dition at  the  end  of  eight  months. 

A  similar  test  but  less  severe,  and  therefore  more  nearly 
approaching  conditions  that  may  occur  in  storage  on  a  factory 
scale,  is  the  following  experiment  by  G.  Henschel.^ 

10  to  II  grams  of  commercial  Cyanamid  was  placed  in  a 
thin  layer  on  a  watch-glass  of  about  8  cm.  diameter,  and  set 
in  a  desiccator  jar,  in  which  was  a  beaker  with  concentrated 
sulphuric  acid  and  another  with  distilled  water.  This  provided 
a  constant  circulation  of  moist  air.     In  addition,  for  an  hour 

'  Das  Verhalten  des  technischen  Calciunicyauamides  bei  der 
Aufbewahrung  sowie  unter  dem  Einfluss  von  Kulturboden  und 
Kolloiden.     Inaugural-Dissertation-Univ.  of  Leipzig,  1912. 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         3I 

each  day  during  the  entire  21  weeks  of  exposure,  a  current 
of  air  was  drawn  through  the  desiccator. 


Per  cent. 

Dicyan- 

Weight  of 

increase     Total 

Cyanamid 

diamide 

Urea 

sample 

in  weight  nitrogen 

nitrogen 

nitrogen 

nitrogen 

Original 10.609  S 

—          13-09 

12.031 

0.064 

0.694 

After  21  weeks-    11.343  g 

6.92           12.32 

9-563 

1. 221 

1.460 

Same  corrected 

to  original 

weight — 

—          13-17 

10.224 

1.305 

1.560 

There  is  therefore  no  loss  of  nitrogen,  but  on  the  other 
hand  an  apparent  slight  gain,  probably  due,  in  the  belief  of  the 
experimenter,  to  loss  of  moisture  before  the  weighing  of  the 
sample  for  analysis.  The  total  increase  in  weight  is  6.92  per 
cent.,  which  is  about  the  same  as  the  increase  in  the  factory 
test  at  Jacksonville,  Florida,  described  on  p.  24.  The 
amount  of  derivatives  formed  in  the  latter  case  was  probably, 
therefore,  about  the  same  as  in  the  laboratory  test  by 
Henschel.  The  amount  of  dicyandiamide  formed  is  about 
10  per  cent,  of  the  total  nitrogen,  and  the  urea  is  about  the 
same. 

The  agricultural  significance  of  these  changes  will  be  dis- 
cussed in  a  later  chapter  of  this  volume. 

The  above  are  a  few  of  the  many  records  at  the  command 
of  the  author,  all  of  which  agree  in  showing  that  when  the 
increase  in  weight  is  allowed  for  there  is  no  loss  of  nitrogen 
in  Cyanamid  under  the  ordinary  conditions  of  storage  of  fer- 
tilizer materials. 


CHAPTER  V. 


Decomposition  of  Cyanamid  in  the  Soil. 

FACTORS  INVOLVED. 

When  Cyanamid  is  applied  to  the  soil  as  a  fertilizer  it  must 
undergo  decomposition  before  the  nitrogen  can  be  assimilated 
by  plants.  The  course  of  this  decomposition,  however,  has 
been  in  dispute  since  the  adoption  of  Cyanamid  in  agriculture, 
and  a  great  deal  has  been  written  on  the  subject.  Owing  to 
the  incompleteness  of  many  of  the  reports,  and  the  omission 
of  essential  data,  no  attempt  will  be  made  here  to  review  all 
of  them.  Of  the  recent  work  on  the  subject  the  most  con- 
sistent seems  to  be  that  of  C.  Ulpiani  and  H.  Kappen. 

Experiments  of  Ulpiani. — In  1908  Ulpiani  reported  the 
results  of  some  experiments^  that  indicate  the  difficulties  sur- 
rounding the  solution  of  this  important  question.  The  results 
of  these  tests  are  summarized  in  the  table  on  page  33. 

Aqueous  solutions  were  used  containing  0.5  per  cent,  pure 
cyanamide,  together  with  various  added  materials  as  noted. 
Calcium  was  added  in  the  form  of  calcium  hydroxide,  two 
equivalents  to  one  of  cyanamide.  By  "secondary  products" 
is  meant  dicyandiamide,  urea,  and  traces  of  amidodicyanic 
acid  and  ammonia,  amounting  to  33  per  cent,  of  the  total 
nitrogen  present.  Soil  was  added  where  shown  in  the  table, 
in  the  proportion  of  10  grams  to  100  cc.  of  solution.  The 
"nutritive  substance  for  bacteria"  consisted  of  0.05  per  cent, 
potassium  phosphate,  o.oi  per  cent,  asparagine  and  o.oi  per 
cent,  glucose.  Bacteria  were  introduced  into  flasks  3  to  8  by 
extracting  soil  with  the  water  to  be  used  to  make  the  cyana- 
mide solution.  No  bacteria  were  present  in  flasks  i  and  2. 
0.4  per  cent,  chloroform  was  present  in  flasks  7  and  8.  Deter- 
minations for  cyanamide  nitrogen  in  the  solutions  were  made 
at  frequent  intervals.  The  percentages  of  cyanamide  decom- 
posed in  4  and  8  weeks  respectively  are  shown  in  the  table : 
1  Gaz.  Chim.  Ital.,  1908,  II,  No.  4,  358-417. 


CYANAMID — manufacture:,    CHE:MISTRY    AND    USES         33 


Flask  Calcium 

Secondary 
products 

Soil 

Nutritive 

for 
substance 
bacteria 

Per  cent,  of  cyanamide 
decomposed 

Chloroform   4  wks.    8  wks. 

I. 

Absent 

Present 

Absent 

Absent 

Absent 

0.63 

0.81 

2. 

Present 

*' 

«• 

'« 

" 

53-25 

73-02 

3. 

Absent 

(t 

Present 

Present 

(( 

50.50 

83-03 

4- 

Present 

" 

" 

" 

" 

83.00 

100.00 

5. 

Absent 

Absent 

" 

" 

" 

6.84 

16.72 

6. 

Present 

(( 

" 

" 

" 

40.62 

— 

7. 

Absent 

" 

*' 

" 

Present 

7.58 

15.52 

8. 

Present 

(( 

Absent 

li 

«t 

41.04 

— 

Flasks  I  and  2  were  not  inoculated  with  bacteria.  Flask  i 
therefore  shows  that  a  solution  of  cyanamide,  in  the  presence 
of  its  derivatives,  is  not  decomposed  even  upon  months  of 
standing.  The  mere  addition  of  lime  in  sterile  conditions 
causes  a  rapid  decomposition  of  cyanamide.  The  effect  of 
lime  is  shown  throughout  by  comparing  the  even-numbered 
flasks  with  the  odd-numbered  flasks. 

Flask  7  shows  that  under  sterile  conditions,  in  the  absence 
of  lime,  a  small  amount  of  soil  causes  a  small  amount  of 
decomposition.  Flask  5,  which  differs  from  flask  7  only  in 
the  fact  that  the  sterilizing  agent,  chloroform,  was  omitted, 
shows  that  the  presence  of  bacteria  had  no  effect  whatever 
upon  the  decomposition.  The  same  thing  is  shown  by  com- 
paring flasks  6  and  8,  in  which  lime  was  present. 

The  larger  values  obtained  in  flasks  2,  3  and  4  seem  to  be 
related  in  some  way  to  the  presence  of  secondary  products, 
that  is,  dicyandiamide,  urea,  and  possibly  amidodicyanic  acid 
and  ammonia.  Flasks  i  and  2  were  both  uninoculated,  hence 
the  larger  decomposition  of  flask  2  as  compared  with  flasks 
6  and  8  must  be  due  to  the  simultaneous  action  of  calcium 
and  secondary  products  of  cyanamide.  A  separate  experi- 
ment showed,  in  fact,  that  the  presence  of  0.085  per  cent, 
ammonia  in  a  solution  of  pure  cyanamide  containing  0.43 
per  cent,  cyanamide  effected  the  complete  removal  of  the 
cyanamide  in  3  months  at  30°  C,  while  the  cyanamide  without 
an  ammonia  addition  remained  constant. 

It  is  interesting  to  compare  flask  i  with  flask  3.  These 
differ  in  two  respects,  presence  of  soil  and  presence  of  nutri- 


34         CYANAMID — MANUFACTURE),    CHEMISTRY    AND    USES 

tive  substance.  Now  soil  in  the  presence  of  secondary  products 
may  be  expected  to  act  similarly  to  soil  in  the  absence  of 
secondary  products,  that  is,  the  soil  should  determine  in  flask 
3  about  7  per  cent,  of  decomposition  more  than  occurred  in 
flask  I.  The  presence  of  nutritive  substance  is  therefore 
probably  in  this  case  the  controlling  factor,  but  not  nutritive 
substance  alone/  but  nutritive  substance  in  combination  with 
soil  and  cyanamide  derivatives.  It  is  quite  possible  that  a 
bacterial  decomposition  that  does  not  take  place  in  the  pres- 
ence of  cyanamide  alone  may  take  place  if  other  nitrogenous 
substances  are  present  which  are  capable  of  being  attacked 
by  bacteria.  In  fact,  Ulpiani  determined  by  separate  experi- 
ments that  the  soil  bacteria  employed  by  him  were  not  able 
to  decompose  pure  cyanamide,  but  that  they  grew  very  readily 
in  impure  dicyandiamide  solutions,  while  the  experiments  of 
Kappen  show  that  micro-organisms  do  take  part  in  the  decom- 
position in  the  presence  of  nutrient  solutions  and,  with  the 
exception  of  special  fungi,  in  non-sterilized  soil.  The  effect 
of  micro-organisms  and  of  glucose  used  as  a  nutritive  sub- 
stance is  shown  by  the  following  experiment  of  Kappen.^ 

One  hundred  grams  of  a  sand  soil  of  low  activity  was  treated 
with  50  cc.  cyanamide  solution  containing  33  mg.  of  cyanamide 
nitrogen.  The  same  treatment  was  given  another  100  grams, 
but  glucose  was  added.  In  another  case  no  glucose  was  added, 
but  the  soil  was  inoculated  with  cyanamide-splitting  clado- 
sporium,  a  special  fungus,  occurring  in  some  soils.  The  sub- 
sequent content  of  cyanamide  nitrogen  is  shown  in  the  fol- 
lowing table: 

Without 
Cyanamide  glucose 

nitrogen  in  With  Without  with 

milligrams  glucose        glucose   cladosporium 

Applied 33-00  33.00  33.00 

Analysed  immediately 31-75  32.04  32.48 

After  I  day 25.87  23.70  — 

After  2  days 23.52  21.16  4.70 

After  3  days 19-69  17-93  0.00 

After  7  days 8.33  12.55           - 

After  9  days 0.00  10.29  — 

*  Zentr.  fur  Kunstdiinger  Ind.  XVII,  251,  191 2. 


CYAN  AM  ID — manufacture:^    CHEMISTRY    AND    USES         35 

It  will  be  noticed  that  on  the  third  day  the  amount  of 
cyanamide  that  had  been  decomposed  was  about  the  same 
whether  glucose  were  present  or  not,  in  fact  there  seems  to 
be  slightly  more  decomposition  when  the  glucose  was  omitted, 
though  this  is  probably  accidental.  At  the  end  of  9  days, 
however,  the  glucose  treated  sample  was  entirely  decomposed, 
while  the  untreated  sample  still  contained  about  one-third  of 
the  original  cyanamide.  Cladosporium  in  the  presence  of  soil 
caused  a  rapid  decomposition,  complete  in  3  days.  It  is  at 
once  evident  that  the  sand  soil  used  did  not  contain  appre- 
ciable amounts  of  cladosporium,  or  the  decomposition  would 
have  been  more  rapid  in  the  first  two  cases.  During  the  first 
three  days  the  samples  with  and  without  glucose  behaved  very 
much  alike,  hence  the  same  processes  were  taking  place,  and 
these  were  probably  chemical;  then,  however,  the  glucose 
treated  sample  became  suddenly  very  active,  and  this  prob- 
ably represents  the  beginning  of  bacterial  participation. 

It  should  be  noted  in  the  above  experiment  that  the  concen- 
tration of  cyanamide  applied  was  0.022  per  cent.,  as  compared 
with  the  0.5  per  cent,  used  by  Ulpiani.  It  is  likely  that  the 
latter  concentration  is  too  great  to  permit  bacterial  activity, 
except  under  the  most  favorable  circumstances  and  then  only 
with  certain  bacteria.  The  quantity  of  cyanamide  applied  by 
Kappen  is  equivalent  to  about  600  pounds  of  nitrogen  per 
acre  half-foot  of  soil.  In  agriculture,  60  pounds  per  acre  is 
a  maximum  that  is  seldom  exceeded. 

Kappen  succeeded  in  isolating  pure  cultures  of  five  fungi 
capable  of  decomposing  cyanamide;  two  of  them,  penicillum 
brevicaule,  and  the  cladosporium  mentioned  above,  grew  even 
in  2  per  cent,  solutions,  but  the  others  required  lower  concen- 
trations. It  is  therefore  difficult  to  estimate  the  importance 
of  these  special  fungi  to  this  problem.  It  is  certain  that  they 
do  not  occur  commonly  in  all  soils  (those  used  by  Ulpiani 
for  instance  and  the  ordinary  soils  of  Kappen)  to  any  great 
extent,  and  it  is  doubtful  if  they  ordinarily  have  much  to  do 
with  Cyanamid  decomposition  in  the  soil. 


36         CYANAMID — MANUFACTURE),    CHEMISTRY    AND    USES 

Ulpiani  explains  their  action  as  follows:  The  fungi  may 
decompose  the  glucose,  when  it  is  present,  with  the  produc- 
tion of  various  aldehydic  substances,  which,  according  to  well- 
known  chemical  reactions  unite  with  the  cyanamide  with  for- 
mation of  compounds  of  the  type  R.CH :  N.CN.  It  is  also 
possible  that  the  fungi  produce  various  products  of  metabolism 
which  are  able  to  react  with  cyanamide  and  so  neutralize  it, 
probably  in  the  manner  of  the  formation  of  antitoxins.  He 
cites  in  support  of  this  theory  the  well-known  ability  of 
penicillum  brevicaule  to  grow  in  the  presence  of  arsenical 
substances.^ 

The  above  experiments  are  in  agreement  with  many  others 
by  Kappen,  as  well  as  with  the  experiments  of  Ashby,^ 
Behrens,^  Stutzer  and  Reis*  and  others,  which  show  that  bac- 
teria are  active  in  some  stage  of  the  process. 

From  these  experiments  of  Ulpiani,  Kappen  and  others,  the 
following  facts  are  evident:  i.  A  solution  of  pure  cyanamide 
in  the  absence  of  other  substances  is  quite  stable,  and  is  not 
decomposed  by  ordinary  soil  bacteria.  2.  A  solution  of  pure 
cyanamide  may  be  decomposed  by  certain  special  fungi. 
3.  A  solution  of  cyanamide  in  sterile  conditions  is  decomposed 
by  lime,  by  ammonia,  and  by  soil.  4.  A  solution  of  cyanamide 
is  decomposed  by  soil  more  rapidly  in  non-sterile  conditions 
than  in  sterile  conditions,  provided  the  concentration  is  not 
too  great. 

The  course  of  the  decomposition  of  cyanamide  solutions 
by  lime  is  very  complex  (see  also  p.  28)  and  leads  to  the 
formation  of  a  mixture  of  urea,  dicyandiamide,  amidodicyanic 
acid,  ammeline,  melammine  and  other  complex  derivatives.  On 
the  other  hand,  the  decomposition  of  cyanamide  by  soil  is  a 
simple  hydrolysis  in  accordance  with  the  equation : 

-    ^  B.  Gosio,  Studio  suUa  Bioreazione  dell  'arsenico  tellurio  e  selenio. 
Roma,  Tip,  Mantellate,  1907. 
2  Zent.  Bakt.  XX,  704,  (1908)  ;  XX,  281,  (1908). 
'Jahrs.  f.  Agrik.  121,  (1905). 
*  Jour.  f.  Landw.  Vol.  58,  65,  (1910). 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         37 

CN.  NH,  +  H,  O  =    0C<; 

The  formation  of  urea  is  practically  quantitative,  and  is 
determined  ordinarily  solely  by  physico-chemical  means,  with- 
out the  participation  of  organisms.  It  will  be  shown  later  that 
the  transformation  of  the  urea  to  ammonia  is  probably  effected 
by  bacteria. 

FIRST  STAGE  OF  DECOMPOSITION. 

The  form  in  which  the  nitrogen  exists  in  Commercial 
Cyanamid,  neglecting  for  the  moment  the  alterations  produced 
in  storage,  is  calcium  cyanamide.  It  has  been  known  for 
many  years  that  this  salt  is  not  stable  in  aqueous  solution  but 
immediately  hydrolyzes  to  acid  calcium  cyanamide  and  calcium 
hydroxide : 

2CN.  NCa  +  H,0  =  (CN.  NH)2Ca  +  Ca  (OH), 

Moreover,  all  investigators  agree  that  the  acid  calcium 
cyanamide  has  but  an  ephemeral  existence  in  the  soil;  when 
applied  in  normal  fertilizer  doses  the  calcium  quickly  abandons 
the  cyanamide.  Lohnis  attributes  this  action  to  the  effect  of 
carbon  dioxide  in  the  soil  solution,  precipitating  the  calcium 
as  carbonate  and  setting  free  the  cyanamide: 

(CN.NH),Ca  +  CO,  =  2CN.NH,  +  CaC03 

Kappen  considers  the  removal  of  calcium  as  a  physical 
process  of  absorption  in  the  soil,  with  simultaneous  hydrolysis 
to  free  cyanamide: 

(CN.NH),  Ca  -f-  2H,0  =  2CN.  NH,  +  Ca(OH),. 

He  found,  for  instante,  that  when  200  grams  of  clay  soil  was 
shaken  with  250  cc.  of  a  solution  of  lime-nitrogen  containing 
47.8  mg.  calcium  and  62.2  mg.  nitrogen,  39  per  cent,  of  the 
calcium  and  only  5  per  cent,  of  the  nitrogen  was  absorbed  by 


38         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

the  soil  in  one  hour.  Such  a  fertilization,  however,  amounts 
to  560  pounds  nitrogen  per  acre  half-foot  of  soil,  a  quantity- 
far  in  excess  of  any  ever  used  in  agriculture.  The  quantity 
of  calcium  absorbed  in  one  hour  in  this  test  is  equivalent  to 
600  pounds  CaO  per  acre  half-foot  of  soil. 

Ulpiani  regards  the  change  as  taking  place  with  the  inter- 
mediate formation  of  calcium  cyanamide  carbonate: 

(CN.  NH),Ca  +.  CO2  =  CN.  NH,  -f  CaCN,CO,, 
CaCN^CO,  +  H,0  =  CN.  NH,  +  CaC03 

Whatever  the  mechanism  of  this  hydrolysis  there  is  no 
question  but  that  the  result  is  free  cyanamide,  and  conse- 
quently the  following  investigations  on  the  decomposition  of 
cyanamide  in  the  soil  were  made  with  the  free  cyanamide, 
CN.NH2. 


SECOND  AND  THIRD  STAGES  OF  DECOMPOSITION. 

The  following  experiment  by  Ulpiani^  was  made  to  deter- 
mine the  rate  of  decomposition  of  cyanamide:  100  grams  of 
earth  carefully  dried  at  laboratory  temperature,  and  sieved 
through  a  screen  with  holes  of  i  mm.  diameter,  was  placed  in 
a  glass  tube  and  to  it  was  added  20  cc.  of  a  solution  of  pure 
cyanamide  containing  4.2  per  cent,  cyanamide.  The  liquid 
reached  almost  to  the  bottom  of  the  tube,  hence  the  soil  was 
not  quite  saturated.  A  series  of  tubes  so  prepared  was  stop- 
pered with  cork  and  set  in  a  thermostat  at  28°  C.  After 
various  periods  of  time  the  content  of  cyanamide  remaining  in 
the  tubes  was  determined  as  follows :  80  cc.  of  distilled  water 
was  added  and  thoroughly  stirred  with  the  contents  of  the 
tube.  After  exactly  an  hour  the  contents  were  filtered  with 
suction.  Of  the  filtrate  (about  70  cc),  two  portions  of  25  cc. 
each  were  analyzed  for  cyanamide.  The  following  results 
were  obtained : 

1  Gaz.  Chim.  Ital.  XL,  Parte  i,  1910. 


CYANAMID — manufacture:,    CHE:MISTRY    AND    USES         39 


Initial 

After  ]4-  liour  . 
After  6  hours . 
After    I  day 


Quantity  of  cyanamide 
Milligrams 

84.0 

79-2 

75.8 

65.9 


After    3  days 52.5 

After    5  days 40.9 

After    7  days 29.8 

After    9  days 22.6 

After  II  days 18.4 

After  15  days lo.o 

After  18  days cxd.o 

The  values  obtained  are  plotted  in  Fig.  2.     It  is  seen  that 
the  removal  of  cyanamide  from  the  soil  solution  is  a  maximum 


Pays   after  apphcaf /on 

RATE  OF  REMOV/^L  O?  CYANAMIDE 
FROU5OIL  SOLUTION, 

Fig.  2. 

in  the  first  few  moments  of  contact.     This  probably  corre- 
sponds to  an  initial  period  of  absorption.     It  is  evident,  how- 
4 


40         CYANAMID — MANUFACTURE:,    CHEJMISTRY    AND    USJ^S 

ever,  that  the  cyanamide  is  not  removed  solely  by  a  process 
of  absorption,  since  it  is  characteristic  of  absorption  processes 
that  a  state  of  equilibrium  is  usually  reached  between  the  sub- 
stance in  solution  and  in  the  absorbing  surfaces  within  a  day. 
The  substance  that  is  being  absorbed  never  disappears  entirely 
from  the  solution.  In  the  present  experiment,  the  reaction 
proceeds  to  complete  disappearance  of  the  cyanamide.  The 
rate  of  removal  of  cyanamide  is  practically  constant  after  the 
first  9  days,  and  shows  no  tendency  to  become  zero  thereafter, 
as  it  would  if  an  equilibrium  were  being  approached.  Such 
rapid  removal  of  the  cyanamide  to  the  very  end  of  the  experi- 
ment can  be  due  only  to  chemical  conversion  of  the  cyanamide 
to  other  forms. 


INFLUENCE  OF  CONCENTRATION. 

The  following  experiment  was  made  by  Ulpiani  to  deter- 
mine the  effect  of  varying  the  concentration  of  cyanamide. 
In  each  of  a  series  of  glass  tubes  was  placed  lOO  grams  of 
soil,  which  was  covered  with  25  cc.  of  a  solution  of  cyanamide 
at  various  concentrations.  At  the  end  of  3  days  and  at  the 
end  of  10  and  30  days,  certain  tubes,  as  shown  in  the  table, 
were  taken  out,  thoroughly  mixed  with  75  cc.  water  and  after 
standing  one  hour  were  filtered  with  suction,  and  cyanamide 
was  determined.    The  following  results  were  obtained: 


Initial  quantity 
of  cyanamide 

-,         Final  quantity  of 

After             After 
3  days          10  days 

cyanamide 

After 
30  days 

Absolute 

quantity 

converte'd 

in  3  days 

Mg. 

Concen- 
tration 
Per  cent. 

Mg. 
in  25  cc. 

Percentage 
converted 
in  3  days 

I 

25.0 

trace 

— 

— 

25.0 

100 

2 

50-0 

251 

— 

— 

24.2 

49 

3 

75.0 

43.5 

— 

— 

31.4 

42 

4 

lOO.O 

60.0 

— 

— 

40.0 

40 

5 

125.0 

84.0 

— 

— 

41.0 

33 

6 

150.0 

103.4 

— 

— 

46.5 

31 

9 

225.0 

171.3 

110.8 

13.4 

53.7 

24 

12 

300.0 

231.8 

156.8 

40.3 

68.2 

23 

15 

375.0 

302.4 

209.1 

60.5 

72.6 

19 

18 

450.0 

352.8 

245.2 

67.2 

97.2 

21 

21 

525-0 

420.0 

289.8 

71.4 

105.0 

20 

CYANAMID — manufacture:,    CHEMISTRY    AND    USES         4I 

In  Fig.  3  is  plotted  the  percentage  of  the  cyanamide  removed 
with  increase  of  concentration.  This  percentage  is  a  maximum 
at  the  lower  concentrations,  but  decreases  as  the  concentration 
increases,  until  finally  a  steady  value  of  about  20  per  cent,  is 
reached,  when  the  amount  of  cyanamide  disappearing  in  a 
given  time  is  constant.  The  fact  that  this  curve  is  approxi- 
mately logarithmic  indicates  that  the  primary  action  is  one  of 
absorption,  since  it  is  well-known  that  the  more  dilute  the  solu- 
tion the  greater  is  the  percentage  of  substance  taken  up  by  the 
absorbing  surfaces,  and  that  as  the  concentration  of  solution 


too  9 


EFFECT  OF  CONCENTRATION 
ON  REMOVAL  OF  CYANAMIDE 
FROM  SOIL  SOLUTION. 


increases  a  condition  of  equilibrium  is  reached  and  the  ratio 
of  the  concentrations  in  the  absorbing  surfaces  and  in  the 
solution  becomes  constant. 

Fig.  4  shows  the  absolute  quantity  of  cyanamide  removed  as 
the  concentration  increases.  It  is  practically  directly  propor- 
tionally to  the  concentration.  This  curve  shows  the  same 
fact  as  the  curve  in  Fig.  4,  namely,  that  the  ratio  of  the  con- 
centrations in  the  absorbing  surfaces  and  in  the  solution  is 


42         CYANAMID — MANUl^ACTURE,    CHEMISTRY   AND   USES 

a  constant,  a  fact  highly  characteristic  of  absorption  pro- 
cesses. 

In  this  experiment  also,  the  cyanamide  finally  disappears 
entirely  from  the  solution  in  the  course  of  time,  and  hence, 
chemical  conversion  occurs  along  with  the  absorption 
phenomena. 

Taking  all  the  above  facts  together,  it  is  easy  to  under- 
stand that  in  the  initial  period  of  contact  between  the  cyanamide 
solution  and  the  soil  there  is  a  withdrawal  of  cyanamide  mole- 
cules from  the  solution,  and  a  concentration  of  molecules  in 


Gleams   Cyart<xm/€/e  app/ted 
p6f  Zoo  grants  so//. 


Fig.  4. 

the  limiting  stratum  between  the  solution  and  the  surface  of 
the  solid  soil  particles.  Along  with  and  subsequent  to  this 
absorption  process  there  is  a  chemical  conversion  of  cyanamide 
molecules,  by  catalytic  action  of  soil  colloids,  as  we  shall  show 
later,  the  products  of  the  reaction  being  removed  continually 
and  being  replaced  by  new  molecules  of  cyanamide  in  the  limit- 
ing stratum. 


CYANAMID — MANUFACTURE,    CHE:MISTRY    AND    USES         43 

That  bacteria  could  take  no  part  in  the  present  experiment 
is  evident,  since  micro-organisms  cannot  live  in  the  very  con- 
centrated solutions  employed. 

INFLUENCE  OF  TEMPERATURE. 

Experiments  carried  out  in  a  similar  manner  with  lOO  grams 
of  soil  and  20  cc.  of  solution  containing  4.2  per  cent,  cyanamide 
at  various  temperatures  gave  the  following  results: 

At  0°  At  12°  At  30° 


Initial  quantity  of  cyanamide . .  • 

.     84  mg. 

84  mg. 

84  mg. 

Quantity  present  after  2  days-  •  • 

77 

69 

51 

it                      a                a        ^       " 

•     73 

59 

23 

"              "          "      6    '*     ... 

.     69 

44 

18 

(«              <(          *'    II     '*     . . . 

•     53 

33 

trace 

The  velocity  of  the  reaction  increases  with  the  temperature, 
but  even  at  0°,  where  micro-organic  life  is  practically  at  a 
standstill,  there  is  a  conversion  of  about  3.5  mg.  of  cyanamide 
per  120  grams  of  damp  soil  per  day. 

INFLUENCE  OF  SOIL  AT  100°  C. 

Two  flasks,  one  containing  icx)  cc.  of  a  solution  with  21  per 
cent,  cyanamide,  the  other  icxD  cc.  of  21  per  cent,  cyanamide 
solution  and  500  grams  of  soil,  were  heated  in  a  Koch's  oven 
at  100°  C.  for  six  hours.  After  cooling,  400  cc.  of  water  was 
added  to  each,  and  after  agitation  and  filtering,  analyses  were 
made.  In  the  flask  without  soil  there  was  still  a  large  quantity 
of  cyanamide  present  and  considerable  dicyandiamide.  In  the 
flask  with  soil,  however,  there  was  no  cyanamide  or  dicyandia- 
mide remaining  after  the  treatment,  but  abundant  quantities  of 
urea.  Under  these  conditions  it  is  probable  that  the  conver- 
sion to  urea  is  quantitative.  The  reaction  must  be  one  of 
hydrolysis  in  accordance  with  the  equation. 

CN.  NH,  -f  H,0  -*  0C< 


44         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

NATURE  OF  PRODUCTS  FORMED  IN  SOU  AT  ORDINARY 
TEMPERATURES. 

The  formation  of  dicyandiamide  is  always  accelerated  by  the 
action  of  heat,  whether  in  solutions  of  cyanamide,  or  in  solu- 
tions of  cyanamide  treated  with  lime,  ammonia  or  other  weak 
bases.  Since  there  is  no  formation  of  dicyandiamide  when 
cyanamide  is  heated  with  soil,  as  shown  in  the  experiment  on 
page  43,  there  will  evidently  be  none  formed  at  ordinary  tem- 
peratures.    This  is  verified  in  the  following  two  experiments. 

Four  kg.  of  soil  in  a  balloon  flask  was  sterilized  on  three 
successive  days  by  heating  for  an  hour  each  day  in  an  auto- 
clave at  ioo° ;  then  was  introduced  into  the  flask  800  cc.  of  a 
solution  containing  4.2  per  cent,  cyanamide.  The  flask  was 
stoppered  and  kept  in  a  thermostat  at  25°  for  18  days.  After 
agitation  with  3,200  cc.  water  for  an  hour,  and  filtering  with 
suction,  total  nitrogen  and  cyanamide  nitrogen  were  deter- 
mined.    The  results  were  as  follows : 

Grams 

Initial  nitrogen 2.492 

Nitrogen  absorbed  in  soil i- 154 

Nitrogen  in  solution  as  cyanamide 0.671 

**  "     not  cyanamide 0,667 

"  "as  dicyandiamide none 

After  the  removal  of  the  cyanamide,  and  concentration  on  the 
water  bath,  addition  of  nitric  acid  produced  an  abundant  pre- 
cipitate of  nitrate  of  urea,  which  on  recrystallization  showed  a 
melting  point  of  140°.  This  experiment  shows  that  under 
sterile  conditions  the  product  of  cyanamide  conversion  is  prob- 
ably entirely  urea. 

Under  natural  conditions,  there  is  little  doubt  but  that  the 
urea  is  rapidly  converted  in  the  soil  into  ammonium  com- 
pounds. It  was  desirable  therefore  to  learn  how  closely  the 
action  of  cyanamide  resembled  that  of  ammonium  carbonate 
in  the  soil.  In  a  balloon  flask  containing  11  kg.  of  soil  was 
added  200  cc.  of  solution  containing  4.2  per  cent,  pure  cyana- 
mide; and  in  another  flask  with  11  kg.  of  soil  was  added  200 
cc.  of  solution  containing  9.6  per  cent,  ammonium  carbonate, 


CYANAMID — manufacture:,    CHEMISTRY    AND    USES         45 

equivalent  to  the  amount  of  cyanamide  used.  Each  flask  was 
equipped  with  connections  permitting  a  current  of  air  to  pass 
through  the  flask,  and  then  through  a  bottle  of  dilute  sulphuric 
acid  to  catch  any  ammonia  evolved  in  the  flask.  The  balloon 
flasks  were  held  in  a  thermostat  at  25°  for  22  days,  at  the  end 
of  which  time  800  cc.  water  was  added.  After  shaking  and 
standing  an  hour  and  filtering  with  suction,  tests  showed  that 
there  was  no  cyanamide  or  dicyandiamide  present  in  the  flask 
to  which  cyanamide  had  been  added.  Determinations  were 
made  for  total  nitrogen,  ammoniacal  nitrogen  and  nitric  nitro- 
gen in  the  solution. 

The  following  values  were  obtained: 

Soil  plus 
Soil  plus  ammonium 

cyanamide  carbonate 

mg.  mg. 

Initial  nitrogen 560  560 

Final  nitrogen  absorbed  by  soil. 450  420 

Final  nitrogen  remaining  in  solution  : 

Ammoniacal 60  70 

Nitrate 9  70 

Cyanamide o  — 

Dicyandiamide o  — 

Undetermined 41  o 

The  sulphuric  acid  in  the  bottles,  through  which  bubbled  the 
air  leaving  the  flasks,  was  unchanged,  hence,  no  ammonia 
escaped  from  the  soil. 

Since  the  41  mg.  of  undetermined  nitrogen  in  the  solution 
from  the  cyanamide  flask  was  not  cyanamide,  dicyandiamide, 
ammonia  or  nitrate  nitrogen,  it  must  have  been  urea,  in  accord- 
ance with  the  previous  experiment.  The  conversion  of  the 
urea  to  ammonium  salts  was  therefore  not  quite  complete.  The 
conversion  of  ammonium  salts  to  nitrates  was  also  less  than 
the  conversion  in  the  case  of  ammonium  carbonate.  The 
amount  of  ammoniacal  nitrogen  in  solution  is  practically  equal 
in  the  two  flasks.  It  is  evident,  therefore,  that  in  both  cases 
the  absorbed  nitrogefl  exists  in  the  soil  in  the  state  of  am- 
monium salts,  and  these  are  in  equilibrium  with  the  ammonium 
salts  in  the  solution.     Since  the  soil  was  not  sterilized  and  low 


46         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 


concentrations  of  cyanamide  were  used,  and  large  quantities  of 
ammonia  were  formed,  it  is  very  likely  that  bacteria  partici- 
pated in  the  decomposition  by  reacting  upon  the  urea  and 
determining  its  hydrolysis  to  ammonium  salts. 

EFFECT  OF  CHANGING  RATIO  OF  LiaUID  TO  SOIL. 

When  loo  grams  of  air-dried  earth  was  covered  with  20  cc. 
of  cyanamide  solution  practically  all  of  the  soil  was  wetted, 
only  a  little  at  the  bottom  of  the  tube  remaining  dry.  In  this 
condition  the  mass  of  water  may  be  considered  as  being  at  its 
maximum  distension,  each  solid  particle  of  the  soil  being  sur- 
rounded by  a  thin  film  of  liquid.  This  liquid  film  on  the  in- 
side, is  in  contact  with  a  solid  phase,  and  on  the  outer  surface 
with  a  gaseous  phase,  since  the  interstices  of  the  soil  were  not 
filled  with  liquid. 

When  100  grams  of  soil  was  covered  with  50  cc.  of 
cyanamide  solution  the  interstitial  spaces  were  filled  with 
liquid.  There  was  therefore  practically  no  gaseous  phase 
present. 

One  hundred  grams  of  soil  covered  with  100  cc.  of 
cyanamide  solution  was  completely  submerged.  Series  III  in 
the  table  was  thoroughly  shaken  twice  a  day  during  the  test. 
Series  IV  was  not  disturbed  in  any  way.  The  results  obtained 
were  as  follows : 


Series  I 

Series  II 

Series  IV 

20  cc. 

50  cc. 

Series  III 

100  cc. 

not 

not 

100  cc. 

not 

shaken 

shaken 

shaken 

shaken 

mg. 

mg. 

mg. 

mg. 

Initial 

quantity  Cyananiid 

.    84.0 

84.0 

84.0 

84.0 

Quantity 

after    i  day    

•    65.9 

68.0 

71.9 

73-0 

5  days 

•    40.9 

53-7 

58.1 

60.0 

"       9  days 

.    22.6 

47.8 

54.6 

57.1 

'•      15  days 

.     lO.O 

34-8 

46.2 

49.5 

'*      21  days  .  . . . 

.  00.0 

26.7 

35-7 

44.1 

•'      31  days 

.     0.0 

II. 7 

35.2 

36.9 

"     41  days 

.     0.0 

8.4 

18.6 

33.6 

Here  again  we  must  exclude  bacterial  participation,  since  if 
bacteria  were  present  they  should  grow  better  in  the  dilute 
solutions  than  in  the  solution  of  4.2  per  cent,  cyanamide  in 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         47 

Series  I,  yet  in  the  dilute  solutions  the  transformation  is  very 
slow. 

The  above  experiment  shows  that  the  cyanamide  does  not 
react  with  other  soluble  substances  of  the  soil,  for  in  such  case 
the  maximum  activity  should  occur  in  dilute  solutions ;  but  its 
conversion  is  at  a  maximum  when  the  greatest  amount  of 
cyanamide  is  enabled  to  come  in  contact  with  the  solid  sur- 
faces of  the  soil  particles.  This  condition  is  obtained  when 
for  a  given  quantity  of  cyanamide  the  amount  of  liquid  is  a 
minimum,  for  then  the  liquid  film  about  the  solid  soil  particles 
is  its  thinnest,  the  cyanamide  is  closest  to  the  soil,  and  the 
forces  of  surface  tension  are  at  their  maximum. 

INiXUENCE  OF  AERATION. 

In  order  to  determine  whether  oxidation  plays  any  part  in 
the  phenomena,  an  apparatus  was  arranged  so  that  a  current 
of  air  in  one  case  and  a  current  of  hydrogen  in  another  could 
be  conducted  over  the  samples  of  soil  treated  as  before  with 
4.2  per  cent,  cyanamide  solution.  The  treatment  lasted  for  six 
days,  a  portion  of  the  sample  being  withdrawn  in  three  days. 
The  following  results  were  obtained : 

Quantity  cyanamide  present 

Initial  , « »  Per  cent. 

quantity  after  after  Cyanamide  converted  in 

cyanamide  3  days  6  days  , ' > 

Mg.  Mg.  Mg.  3  days  6  days 

Air 168.0  iio.o  22.0  34.0  86.0 

Hydrogen..    168.0  114.0  46.0  32.0  72.0 

There  is  practically  no  difference  in  the  amounts  of  conver- 
sion in  3  days,  and  not  a  great  deal  of  difference  between  the 
amounts  of  conversion  in  6  days.  The  results  do  not  differ 
enough  so  that  it  can  be  said  that  oxidation  plays  any  appreci- 
able part  in  the  change.  The  fact,  therefore,  that  in  all  of  the 
preceding  experiments  the  tubes  were  stoppered  with  cork  and 
sealed  with  paraffin  to  prevent  evaporation  of  water  could  not 
at  any  rate  increase  the  conversion. 


48         CYANAMID — MANUFACTURE),    CHEMISTRY   AND    USE:S 

INFLUENCE  OF  ELECTROLYTES. 

To  determine  the  effect  of  the  presence  of  various  reagents 
on  the  course  of  the  conversion,  an  experiment  was  made  with 
solutions  of  cyanamide  in  balloon  flasks  without  addition  of 
soil,  but  with  various  electrolytes.  The  concentration  of 
cyanamide  in  the  solution  was  0.554  per  cent. ;  the  other  reag- 
ents were  in  the  proportion  of  two  equivalents  to  one 
cyanamide.  The  following  table  shows  the  amounts  of 
cyanamide  remaining  in  solution. 

554  mg.  cyanamide  plus 
After  —  c'a(OH)2         KOH  HNO3         KNO3 

—  weeks 554.0  557.0  556.0  451.0  558.0 

3.3  weeks 554-0  413.0  420.0  254.0  422.0 

8,3  weeks 554.0  369.0  382.0  —  369.0 

13.3  weeks 554.0  331.0  340.0  —  303.0 

28.3  weeks 554-o  182.0  trace  —  trace 

The  very  slow  course  of  the  reactions  as  compared  with 
the  action  of  soil  shows  that  it  is  probably  not  the  soluble 
salts  in  the  soil  that  are  responsible  for  the  hydrolysis  of 
cyanamide  but  the  solid  soil  particles. 

This  confirms  the  conclusion  drawn  on  page  42. 

NATURE  OF  EFFECTIVE  SOIL  CONSTITUENTS. 

In  order  to  determine  whether  the  conversion  of  cyanamide 
is  caused  by  the  gross  solid  particles  of  mineral  matter  in  the 
soil,  or  whether  it  is  due  to  colloids,  or  various  organic  debris, 
the  following  experiment  was  .made.  Soil  was  allowed  to 
stand  a  week  in  contact  with  concentrated  hydrochloric  acid, 
and  was  then  washed  free  of  acid.  A  portion  of  soil  so 
treated  was  saturated  with  sodium  carbonate  solution  and 
then  washed  free  of  alkaline  reaction.  A  fresh  portion  of 
soil  was  calcined  by  heating  in  a  combustion  furnace  in  a 
current  of  oxygen  until  carbon  dioxide  no  longer  escaped. 
These  samples  were  treated  with  cyanamide  solutions  as  in 
previous  experiments,  with  the  following  results: 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES         49 

Final  cyanamide 

Initial  after  after  after 

cyanamide     3  days        6  days        9  days 
mg.  mg.  mg.  mg. 

Ordinary  soil 83.8  52.0  36.0  19.5 

Soil  treated  with  HCl 83.8  63.5  49.1  36.0 

Soil  treated  with  HCl  and  NaaCOg..  83.8  55.5  43.2  46.0 

Soil  calcined 83.8  —  —  77.6 

Each  of  the  above  treatments  has  diminished  the  ability  of 
the  soil  to  convert  cyanamide  to  other  forms.  The  calcined 
soil  has  very  little  power  of  decomposition.  It  is  evident, 
therefore,  that  it  is  not  the  gross,  solid,  mineral  particles  of 
the  soil  that  have  this  power,  but  certain  constituents  of  the 
soil  mass  that  are  destroyed  by  heat.  These  constituents 
belong  to  the  class  of  chemical  compounds  that  form  colloids 
or  disperse  systems  in  the  soil. 

We  will  now  examine  the  results  of  experiments  made  with 
various  materials  that  are  known  to  form  part  of  practically 
all  soils. 

EFFECT  OF  ZEOLITES. 

According  to  Van  Bemmelen^  the  colloids  of  agricultural 
soil  consist  principally  of  amorphous  zeolites  (amorphous 
hydrated  silicates).  These  remain  for  an  indeterminate  time 
in  suspension  in  pure  water,  are  coagulated  by  electrolytes, 
can  be  dried  into  hard  compact  masses,  have  in  the  highest 
degree  the  properties  of  hydrogels,  and  to  their  presence  is 
probably  due  the  greater  part  of  the  absorptive  powers  of 
the  soil.  Since  these  substances  could  not  be  isolated  in  their 
natural  state  it  was  necessary  to  use  certain  crystallized 
zeolites,  as  follows: 

Natrolite  of  Bohemia,  hydrated  metasilicate  of  aluminium 

and  sodium. 
Scolecite  of  Ireland,  hydrated  metasilicate  of  aluminium  and 
calcium. 
1  Landw.  Ver.  Staz.  Bd.  XXXV,  (1888)  p.  69. 


50         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

Analcimite  of  Tyrol,  hydrated  trisilicate  of  aluminium  and 
sodium. 

Cabasite  of  Nova  Scotia,  hydrated  trisilicate  of  aluminium 
and  calcium. 

Each  zeolite  was  ground  in  a  mortar  and  made  to  pass  a 
screen  of  fineness  Kahl.  oo. 

One  hundred  grams  of  each  zeolite  was  placed  in  glass  tubes 
moistened  with  20  cc.  of  a  4.2  per  cent,  solution  of  cyanamide 
(2.8  per  cent,  nitrogen).  A  fifth  tube  without  zeolite  was  used 
as  a  control.  After  12  days  in  a  thermostat  the  solutions  were 
analyzed  with  the  following  results: 

Cyanamide 
Initial  after 

cyanamide  12  days 

grams  grams 

Solution  alone 0.0840  0.0836 

**       natrolite 0,0840  0.0235 

**       scolecite 0.0840  0.0148 

"       analcimo 0,0840  0,0158 

'*       cabasite 0.0840  0.0168 

This  experiment  shows  that  the  crystalline  zeolites  possess 
to  a  high  degree  the  ability  to  transform  the  cyanamide,  from 
which  we  may  conclude  that  the  colloidal  zeolites  as  they  exist 
in  the  soil  must  have  a  still  greater  ability.  The  crystalline 
zeolites,  according  to  Zambonini,^  have  a  structure  analogous 
to  that  of  the  hydrosols,  and  according  to  Von  Weimarn^  may 
act  like  colloidal  substances. 

EFFECT  OF  CARBON. 

Ulpiani  next  desired  to  learn  what  effect  would  be  obtained 
with  a  material  exposing  a  large  surface,  but  of  no  chemical 
activity  towards  cyanamide.  For  this  purpose  a  commercial 
animal  carbon  was  washed  with  hydrochloric  acid  and  then 
with  water  until  free  from  acid,  and  was  dried  in  an  oven  at 
110°  C.  In  order  to  obtain  a  wetting  comparable  to  that  in 
the  experiments  with  soil,  50  grams  of  carbon  was  moistened 

^  Atti.  R.  Ace.  Lincei,  XVIII.  fasc.  II,  1st  Sem,  1909. 

2  Koll.  Zeit.  Vol.  VI,  No,  i,  1910, 


CYANAMID MANUFACTURE,    CHE:MISTRY    AND    USES         5 1 

with  50  cc.  of  4.2  per  cent,  cyanamide  solution.  The  tubes 
were  kept  in  a  thermostat  at  25°  for  different  lengths  of  time. 
Just  before  the  analysis  200  cc.  of  water  was  added,  stirred 
for  exactly  one  hour,  filtered  with  suction,  and  cyanamide  was 
determined  in  the  filtrate.     The  results  were  as  follows: 


Cyanamide  present  Total  nitrogen  in  solution 

nig.  Per  cent.  mg.  Per  cent. 

Beginning 210.0  100  140  100 

After  I  hour 161. 7  77  112  80 

"     6  hours 153.3  73  1^5  75 

"      I  day 132.3  63  102  73 

"     3  days 107.6  51  87  62 

"     5 


7 

9 

15 

22 


96.6  46  89  64 

75.6  36  89  64 

59-3  28  83  59 

8.4  4  64  46 


0.0  o  77  55 

On  the  22nd  day  the  solution  was  distilled  with  magnesia, 
giving  up  66  per  cent,  of  its  nitrogen  as  ammonia.  Hence,  of 
the  55  per  cent,  remaining  in  the  solution  on  the  22nd  day  22 
per  cent,  was  ammoniacal  and  33  per  cent,  ureic  nitrogen.  A 
test  with  nitric  acid  gave  characteristic  crystals  of  urea  nitrate. 
The  experiment  was  repeated,  sterilizing  both  the  carbon 
and  the  cyanamide  solution.  After  2  months  the  following 
results  were  obtained : 

Mg. 

Initial  nitrogen 560 

After  2  months,  ammoniacal  nitrogen 8 

Cyanamide          '*         o 

Dicyandiamide  "         o 

A  test  for  urea  showed  the  presence  of  abundant  quantities. 

These  experiments  with  carbon  show  that  the  decomposition 
of  cyanamide  is  an  hydrolysis  which  is  greatly  accelerated  by 
the  addition  of  catalysers  of  various  kinds. 

EXPERIMENTS  WITH  NATURAL  COLLOIDS. 

The   experiments   of   H.   Kappen^   confirm   in  general   the 
results  obtained  by  Ulpiani.     The   following  experiment  of 
^  Zentr.  f.  Kunstdiinger-Industrie,  XVII,  234-236,  248-251,  1912. 


52         CYANAMID MANUFACTURE,    CHEMISTRY    AND    USES 

Kappen  shows  the  relative  decomposing  ability  of  some  well- 
known  constituents  of  ordinary  soils.  These  materials  were 
selected  so  as  to  diifer  as  widely  as  possible  from  one  an- 
other, so  that  the  effect  of  individual  constituents  might  stand 
out.  Each  substance  was  used  in  its  natural  condition,  with- 
out being  sterilized,  but  ground  to  a  fine  powder.  They  are 
all  in  the  class  of  compounds  that  form  gels  in  the  soil. 

1.  Meadow  iron  ore  from  Guben,  Niederlausitz ;  contain- 

ing considerable  manganese. 

2.  Meadow  iron  ore  from  Otrotschin,  Bohemia;  contains 

no  manganese. 

3.  Earth  of  Siena,  yellow  natural  product  containing  iron 

oxide. 

4.  Umber,  brown  natural  product  containing  iron  and  man- 

ganese oxides. 

5.  Laterite  earth  from  Kamerun. 

6.  Manganese  ore,  principally  manganese  hydroxide. 

7.  Manganese  dioxide. 

8.  Red  Bauxite,  aluminum  hydroxide  gel  containing  iron 

oxide. 

9.  White  Bauxite,  without  iron  oxide. 

10.  Kaolin  from  Meissen. 

11.  Sandy  Kaolin  from  Tiirkismuhl. 

12.  Glass  sand. 

Of  the  above  minerals  No's  i,  2,  3,  4,  6,  7,  8,  9  and  12 
were  used  alone,  while  No.'s  5,  10  and  11  were  mixed  with  an 
equal  quantity  of  glass-sand.  One  hundred  grams  of  each  was 
placed  in  an  Erlenmeyer  flask  and  treated  with  10  cc.  of  a 
0.5  per  cent,  cyanamide  solution,  containing  33  mg.  cyanamide- 
nitrogen.  Immediately  after  the  addition  of  cyanamide,  and 
at  the  end  of  various  periods  of  time  the  content  of  cyanamide- 
nitrogen  was  determined,  with  the  following  results: 


CYANAMID — manufacture:,    CHE:MISTRY    AND    USES         53 


Cyanamide 
nitrogen 

I. 
Iron 
ore 

1. 
Iron 
ore 

Earth 
of  Siena 

4. 
Umber 

5- 
I^aterite 

6. 
Manganese 
hydroxide 

Initial 

33.00 
22.96 

33.00 
33.18 

33.00 
33.51 

33.00 
31.75 

33.00 
34.02 

33.00 
8.00 

After  yi  hour  •  • 

••      I  day 

0.00 

0.00 

32.04 

20.03 

19.40 

0.00 

"     2  days... 

— 

— 

30.87 

13.27 

II.17 

— 

**     3  days  ••• 

.        — 

— 

27.38 

5.92 

— 

— 

"     6  days  ... 

— 

— 

27.04 

0.00 

4.37 

— 

"      7  days  ... 

— 

— 

26.57 

— 

2.82 

— 

Cyanamide       ] 
nitrogen 

Vlanganese 
dioxide 

8. 

Red 

bauxite 

White 
bauxite 

10, 
Kaolin 

II. 
Sandy 
kaolin 

12. 
Glass 
sand 

Initial 

•    33.00 
30.49 

33.00 
32.48 

33.00 
33.04 

33.00 
32.04 

53.00 
32.00 

33.00 
32.00 

After  Yz  hour. . 

"      I  day 

11.76 

29.40 

32.04 

32.04 

26.16 

32.34 

' '      2  days  . . . 

.      0.00 

27.34 

30.86 

31.16 

21.75 

32.34 

"     3  dags..  • 

— 

25.28 

30.57 

30.57 

— 

32.34 

"     6  days... 

— 

19.82 

30.28 

30.28 

13.52 

32.34 

' '     7  days  .  • . 

.        — 

17.68 

29.98 

29.98 

11.76 

32.24 

Of  the  greatest  activity  is  manganese  hydroxide;  second, 
iron  hydroxide  containing  manganese  hydroxide;  and  third, 
iron  hydroxide  free  of  manganese.  The  activity  of  the  next 
most  active  materials  can  properly  be  ascribed  to  their  con- 
tents of  iron  oxide.  The  difference  in  the  activity  of  red  and 
white  bauxite  is  very  likely  due  to  the  difference  in  iron  con- 
tent. The  greater  activity  of  sandy  kaolin  as  compared  with 
kaolin  is  probably  due  to  the  presence  in  the  former  of  zeolitic 
substances,  which,  as  Ulpiani  found,  have  a  high  activity. 

The  low  activity  of  the  kaolin,  considering  the  large  specific 
surface  it  possesses,  suggested  that  the  properties  of  the  vari- 
ous substances  are  not  merely  surface  phenomena,  but  that 
their  specific  chemical  nature  is  of  importance.  Manganese 
hydroxide  and  the  two  iron  ores  were  mixed  with  glass  sand 
in  the  proportion  of  i  gram  to  lOO  grams  sand,  and  a  sample 
of  0.1  gram  manganese  hydroxide  with  lOO  grams  glass  sand. 
These  mixtures  moistened  as  before  with  cyanamide  solution 
containing  33  mg.  nitrogen,  gave  the  following  results,  as  com- 
pared with  the  kaolin  of  the  preceding  experiment : 


54      CYANAMiD — manu:^acture:^  che:mistry  and  use:s 


Glass-sand  plus 


Cyanamide 

nitrogen 

milligrams  Kaolin 

Initial 33.00 

After  15  hours.  ••  — 

'*       2  days 31.16 

•'       3      "    ••-.  30.57 

"       6      "    ....  30.28 


I  per  cent, 
manganese 
hj'droxide 

33.00 

5.06 

0.00 


I  per  cent. 

iron  ore 

No.  I 

33-00 

25-25 

14.78 

8.62 

4.00 


I  per  cent. 

iron  ore 

No.  2 

33- 00 

30.80 
26.48 
22.79 
17.24 


0,1  per  cent, 
manganese 
hydroxide 

33-00 


30.18 
28.33 
25.25 


It  has  been  shown  in  the  preceding  experiment  that  glass 
sand  has  practically  no  activity.  Hence,  o.i  grams  of  man- 
ganese hydroxide  is  more  effective  than  100  grams  of  kaolin. 
The  surface  exposed  by  the  kaolin  is  clearly  much  greater  than 
that  exposed  by  the  smaller  quantities  of  iron  and  manganese 
hydroxides,  and  the  catalytic  activity  of  the  latter  is  therefore 
essentially  connected  with  their  chemical  properties. 

Another  experiment  was  made  to  compare  the  activity  of 
iron  hydroxide,  aluminium  hydroxide  and  silicic  acid.  The 
iron  and  aluminium  hydroxides  were  prepared  by  precipita- 
tion; a  sample  of  each  was  mixed  in  the  undried  condition  with 
4  times  its  weight  of  glass  sand,  the  mixture  then  containing 
2.6  per  cent,  iron  oxide  in  the  one  case  and  1.6  per  cent, 
alumina  in  the  other.  The  aluminium  hydroxide  and  the  pre- 
cipitated silicic  acid  were  dried  and  applied  separately  to  twice 
their  weight  of  glass  sand.  One  hundred  grams  of  each  of 
the  above  mixtures  was  treated  with  20  cc.  of  cyanamide  solu- 
tion containing  33  mg.  of  cyanamide  nitrogen.  The  sub- 
sequent analyses  are  as  follows  : 


Glass-sand  plus 

Iron 

Aluminium 

Cyanamide 

hydroxide 

hydroxide 

Aluminium 

Silicic 

nitrogen  in 

undried 

undried 

hydroxide 

acid 

milligrams 

2.65^  FesOs 

1.6^  AI2O3 

Dried 

Dried 

Applied 

33.00 

33.00 

33.00 

33.00 

After  Yz  hour  •  • 

31.52 

32.48 

32.04 

32.92 

'♦     I    day  ... 

0.00 

32.34 

31.16 

32.63 

"     3    days  .. 

— 

29.56 

29.69 

31.94 

•'     6    days.. 

— 

— 

25.87 

31.08 

Silicic  acid  has  a  slight  ability  to  convert  cyanamide;  and 
aluminium  hydroxide  has  somewhat  more. 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES         55 

To  determine  the  effect  of  varying  quantities  of  iron 
hydroxide  gel,  the  precipitated  undried  hydroxide  was  mixed 
with  glass  sand  in  different  proportions,  and  treated  as  above 
with  the  following  results : 

Cyanamide  Glass-sand  plus  iron  hydroxide  gel  containing 

nitrogen  in  , » . 

milligrams  2.6  ji  FegOa        i-3  5^  FesOa         0.65^  FcgOa  0.26  ?i  Fe2  O3 

Applied 33.00  33.00  33.00  33.00 

After  I  day 0.00  4.31  12.32  23.11 

"     2  days —  0.00  3.69  13.55 

'*     3     "      ••••        —  —  trace  9.85 

"     4     "      —  —  0.00  8.00 

"     5     "      ••••         —  —                     —  5-37 

The  amount  of  conversion,  therefore,  varies  with  the  amount 
of  iron  oxide  present. 

The  same  iron  hydroxide  gel  was  treated  in  different  ways 
to  see  what  effect  would  be  obtained  by  changing  the  form  of 
the  material : 

Precipitated  iron  hydroxide 

Cyanamide  Dried  Heated  in 

nitrogen  in  5  hrs.  at  steam  for  Ignited 

milligrams  Untreated  io5°C  2j^  hrs.  for  %  hrs. 

Applied 33.00  33.00  33.00  33.00 

After  >^  day —  4.31  12.32  — 

After  I  day 0.00  0.00                    6.46  14-47 

"     2  days —  —                      1.57  6.16 

*'     3    **     —  —  0.00  4.00 

•*     4    '•     _  _                      _  1.84 

"     5    "     —  —                       —  o-oo 

The  untreated  iron  hydroxide  has  the  most  activity,  which  is 
decreased  somewhat  by  steaming  and  greatly  decreased  by 
ignition. 

To  determine  the  effect  of  iron  oxide  in  the  condition  of  a 
hydrosol,  250  cc.  of  iron  oxide  sol  containing  0.8  per  cent,  iron 
oxide  was  treated  with  1.25  grams  cyanamide.  The  solution 
remained  clear  and  fluid  during  the  course  of  the  experiment. 
For  the  determinatiou  of  cyanamide,  10  cc.  of  the  clear  solu- 
tion was  pipetted  off,  flocculated  with  ammonium  nitrate  and 
after  dilution  and  filtration,  treated  in  the  usual  manner.  The 
following  results  were  obtained: 
5 


56         CYANAMID — manufacture:,    CHEMISTRY    AND    USES 

Cyanamide 

nitrogen  in  Iron  oxide  sol. 

milligrams  (0.8  per  cent.  Fco  O3) 

Applied 33.04 

After  18  hours 27.77 

' '       2  days 22.40 

"       4  days 10.08 

The  condition  of  sol  is  favorable  to  the  conversion,  but  not  as 
favorable  as  the  condition  of  gel  since  the  dilution  of  the 
cyanamide  hinders  the  reaction. 

In  order  to  determine  whether  or  not  calcium  cyanamide 
reacts  as  readily  as  cyanamide,  a  quantity  of  lime-nitrogen  con- 
taining 33  mg.  of  cyanamide  nitrogen  was  added  to  lOO  g  of  a 
mixture  of  sand  with  equal  weights  of  manganese  hydroxide, 
and  iron  ores  No.  i  and  2,  (see  page  52).  After  24  hours 
the  quantities  of  cyanamide  nitrogen  remaining  were: 

Milligram 

Manganese 0.00 

Iron  ores  No.  i  and  No.  2 0.00 

Glass-sand    29. 18 

With  cyanamide,  glass-sand  left  32.34  mg.  in  solution  after  i 
day.  The  presence  of  the  lime  in  the  lime-nitrogen  evidently 
hastens  the  decomposition  of  the  cyanamide. 

The  effect  of  pure,  calcined  iron  oxide,  FegOg,  on 
cyanamide  was  determined  by  mixing  glass  sand  with  5  per 
cent,  of  its  weight  of  iron  oxide,  and  treating  with  cyanamide 
solution  as  in  the  previous  experiments. 

Milligram 

Cyanamide  applied 33-oo 

"  after  I  day    32.42 

'•     3  days 30.63 

"  "     5  days 28.07 

♦♦  *'     8  days 26.56 

Iron  oxide  therefore  has  a  slow  action  as  compared  with  the 
metal  hydroxides  used. 

EXPERIMENT  WITH  STERHIZED  SOU. 

All  of  the  above  experiments  of  Kappen  were  made  with 
unsterilized  materials;  they  therefore  do  not  differentiate 
between   physico-chemical   and  bacterial   processes.     In   this 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES         57 

experiment,  soil  was  sterilized  by  being  held  several  days  in 
an  atmosphere  of  chloroform  vapor,  and  was  compared  with 
untreated  soil  as  in  the  previous  experiments,  with  the  follow- 
ing results: 

With  chloroform       Without  chloroform 
mg.  mg. 

Cyanamide  nitrogen  applied 33.00  33.00 

Cyanamide  nitrogen  after  2  days  ...   23.00  0.00 

The  addition  of  chloroform  to  the  soil  therefore  greatly  hin- 
ders the  decomposition  of  the  cyanamide,  but  does  not  prevent 
it.  It  is  quite  probable  that  in  all  of  the  experiments  made  by 
Kappen,  except  those  where  high  temperatures  were  employed, 
bacteria  participated  in  the  decomposition  of  the  cyanamide 
by  converting  the  urea  into  ammonium  salts,  thus  hastening 
the  hydrolysis  of  the  cyanamide. 

CONCLUSIONS. 

From  the  above  experiments  on  the  conversion  of  cyanamide 
the  following  conclusions  can  be  drawn: 

I.  Calcium  cyanamide  in  contact  with  moist  soil  undergoes 
a  decomposition  to  the  form  of  ammonium  salts  in  three  inde- 
pendent stages.  The  first  stage  is  a  complete  hydrolytic  sepa- 
ration of  the  calcium  from  the  cyanamide,  induced  by  the 
selective  absorption  of  calcium  by  the  soil,  and  its  probable 
precipitation  as  calcium  carbonate.  (See  p.  37).  The  second 
stage  is  a  hydrolysis  of  cyanamide  entirely  to  urea;  the  third 
stage  is  a  transformation  of  urea  to  ammonium  salts. 

II.  The  cyanamide  disappears  from  the  soil  solution  by  two 
processes : 

(a)  Absorption  and  concentration  of  cyanamide  molecules 
in  the  limiting  stratum  between  the  soil  solution  and  the  soil 
particles.  This  takes  place  during  the  first  few  moments  of 
contact.     (See  pp.  37  and  38). 

(b)  Removal  of  l^e  cyanamide  molecules  from  the  limiting 
stratum  by  hydrolysis  to  urea  under  conditions  of  high  surface 
pressure  and  concentration.     (See  p.  40). 

III.  The  greatest  velocity  of  hydrolysis  occurs  when  the 


58         CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES 

ratio  of  soil  solution  to  soil  is  the  least;  that  is,  when  the 
liquid  film  about  the  soil  particles  reaches  its  maximum  dis- 
tension, and  the  cyanamide  molecules  are  in  closest  contact 
with  the  soil  particles  (See  p.  42). 

IV.  The  hydrolysis  to  urea  is  brought  about  in  the  soil  by 
the  catalytic  action  of  certain  colloidal  substances,  of  which 
the  most  effective  are  the  hydroxides  of  manganese  and  iron, 
and  certain  natural  zeolites  (hydrated  meta-  and  tri-silicates 
of  aluminium  and  sodium  or  calcium  (pp.  48-56).  Other 
colloids  occurring  naturally  in  the  soil  have  less  ability  of 
transformation.     Animal   carbon   is  about   as   active  as   soil 

(P-5I)- 

V.  The  soil  loses  its  power  of  effecting  the  transformation 
when  it  is  calcined  or  when  it  is  treated  with  acids  and  alkalies ; 
that  is,  when  the  colloids  are  destroyed.  Upon  addition  of 
the  colloids  again,  it  reacquires  the  property  of  transformation. 

VI.  The  conversion  of  cyanamide  in  sterile  conditions  is 
entirely  to  the  form  of  urea.  The  urea  was  isolated  and  iden- 
tified (pp.43.  44,  50- 

VII.  In  the  hydrolysis  of  cyanamide  to  urea,  micro-organ- 
isms do  not  participate,  because : 

(a)  The  transformation  proceeds  most  rapidly  at  high  con- 
centrations of  cyanamide  and  at  concentrations  far  above  those 
that  support  life  (pp.  40,  43,  and  46). 

(b)  The  transformation  takes  place  with  greatly  increased 
velocity  at  100°  C.  (p.  43). 

(c)  The  transformation  takes  place  in  the  presence  of  anti- 
septics and  sterilized  materials  (pp.  44,  50,  and  56). 

VIII.  Unless  the  greatest  care  is  taken  to  have  perfectly 
sterile  conditions,  the  urea  is  converted  into  the  form  of 
ammonium  salts.  In  ordinary  soil  this  change  is  very  rapid 
(pp.  40,  44,  and  57). 

IX.  The  conversion  of  the  urea  to  ammonium  salts  hastens 
the  hydrolysis  of  cyanamide  to  urea  by  removing  the  end- 
product  of  the  hydrolysis  (p.  57). 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES         59 

X.  While  cyanamide  itself  is  not  directly  utilized  by  ordi- 
nary bacteria,  this  fact  is  of  relatively  little  importance,  since 
the  soil  bacteria  grow  in  the  presence  of  cyanamide  if  urea 
or  some  other  nutrient  substance  is  present;  the  urea  being 
formed  by  physico-chemical  means  from  the  cyanamide.  (See 
pp.  34,  36,  44,  45,  and  57). 

XI.  The  retention  by  the  soil  of  the  nitrogen  formed  from 
cyanamide  is  under  the  form  of  ammonium  salts  (p.  45). 


CHAPTER  VI. 


Retention  of  Cyanamid  Nitrogen  in  Soil. 


The  absorption  and  retention  of  Cyanamid  nitrogen  by  vari- 
ous soil  constituents  has  been  investigated  by  only  a  few 
workers,  and  very  little  has  been  reported  that  can  be  regarded 
as  of  practical  interest.  Such  tests  to  be  of  value  should  be 
made  with  natural  soils,  and  not  with  pure  constituents,  such 
as  ignited  glass-sand,  as  has  been  done  by  some  investigators. 
The  period  permitted  for  absorption  should  be  at  least  one  or 
two  days,  and  the  proportion  of  aqueous  solvent  should  not 
exceed  that  likely  to  occur  in  agricultural  practice,  nor  should 
larger  quantities  of  nitrogen  be  applied  than  are  likely  to  be 
used  by  the  farmer. 

The  retention  of  nitrogen  is  doubtless  due  to  physical  pro- 
cesses, as  well  as  to  chemical  reaction  with  both  the  mineral 
and  organic  constituents  of  the  soil.  (See  pp.  39  and  45). 
Physically,  Cyanamid  nitrogen  is  retained  in  the  soil  by  pro- 
cesses of  absorption  in  the  same  way  as  sodium  nitrate,  or 
other  salts  which  do  not  form  insoluble  compounds  by  chem- 
ical reaction  with  the  soil.  By  chemical  and  biological  pro- 
cesses, however,  Cyanamid  nitrogen  is  quickly  converted  to 
the  form  of  ammonium  salts,  and  these  are  retained  in  the 
soil  in  the  form  of  humic  and  zeolitic  compounds  of  ammo- 
nium. According  to  A.  D.  Hall,  the  weaker  the  solutions  of 
ammonium  salts  applied  the  greater  is  the  percentage  of 
ammonium  absorbed  by  the  soil.^  In  the  field  the  amount  of 
soil  is  so  enormously  in  excess  that  the  absorption  of  ammo- 
nium salts  is  practically  complete. 

While  plants  undoubtedly  have  the  power  of  directly  assimi- 
lating the  urea^  that  is  formed  as  a  transition  product  during 
the  conversion  from  cyanamide  to  ammonium  salts,  the  dura- 
tion of  the  urea  stage  is  probably  very  short  in  the  soil,  and 

1  A.  D.  Hall,  The  Soil,  New  York,  1910,  p.  215. 

2  Jour.  Agr.  Sci.,  Vol.  IV,  Part  3,  p.  282. 


CYANAMID — manufacture:^    CHEMISTRY    AND    USDS         6l 

the  practical  consequences  of  its  brief  existence  are  probably- 
very  slight.  Hutchinson  and  Miller  have  shown  that  ammo- 
nium salts,  also,  are  directly  assimilated  by  plants,^  but  just 
how  effective  such  processes  are  it  is  difficult  to  estimate. 
Practically  there  can  be  no  doubt  but  that  most  of  the 
ammonium  salts  are  converted  to  nitrates  prior  to  their  absorp- 
tion by  the  plant. 

1  Jour.  Agr.  Sci.,  Vol.  IV,  Part  3,  p.  282. 


CHAPTER  VII. 


Nitrification  of  Cyanamid  Nitrogen. 

While  some  of  the  fertilizing  effect  of  Cyanamid  may  be 
due  to  the  presence  of  urea  and  ammonium  salts,  nitrification 
of  cyanamide  and  its  decomposition  products  may  take  place 
very  readily  in  the  soil  under  favorable  conditions,  providing 
the  concentration  of  nitrogen  is  not  too  great.  This  is  shown 
in  an  experiment  by  Wagner,  which  was  carried  out  as 
follows  :^ 

Two  hundred  and  fifty  grams  of  sandy-loam  soil  was  mixed 
with  5  grams  of  marl  and  the  quantity  of  nitrogen  salts  shown 
in  the  table  below.  Each  salt  was  well  mixed  with  2  grams  of 
gypsum  before  application  in  order  to  facilitate  distribution. 
The  mixtures  were  placed  in  cylindrical  glass  vessels  6^^  cm. 
in  diameter  and  17  cm.  high,  moistened  with  75  cc.  water,  and 
covered  with  50  grams  unfertilized  earth.  The  vessels  were 
allowed  to  stand  at  room  temperature  and  the  evaporated 
water  was  replaced  from  time  to  time.  After  12,  20,  and  33 
days  respectively  samples  were  drawn  from  each  series  and 
analyzed  for  nitrate  nitrogen.  After  subtracting  the  figures 
obtained  in  the  unfertilized  control  vessels  the  following 
results  were  obtained: 

With  the  sodium  nitrate 
Nitrate  nitrogen  as  NO  at  loo,  the  other  fertilizers 

(cctti,)  gave  as  nitrate  nitrogen 

After  After  After  After         After       After 

Fertilizer  12  20  33  12  20  33 

application  days  days  days  days  days        days 

0.05  grams  nitrogen  as 

sodium  nitrate....    23.7  23.9  24.7  100  100        100 
0.05  grams  nitrogen  as 
sulphate    of     am- 
monia    20.8          22.5            —             88  94  — 

0.0125   grams  nitrogen 

as  Cyanamid 3.9  5.9  5.9  66  99  96 

0.025  grams      nitrogen 

as  Cyanamid 4.1  9.9  11.2  35  83  91 

0.05  grams  nitrogen  as 

Cyanamid 0.3  6.3  14.9  i  26  60 

^  Landw.  Vers.  Stat.  Vol.  66,  No.  4  and  5,  1907. 


CYANAMID — manufacture:,    CHEMISTRY    AND    USES         63 

0.0125  grams  nitrogen  per  250  grams  of  soil  is  equivalent 
to  a  fertilization  of  about  90  pounds  of  nitrogen  per  acre. 
With  this  large  application,  even,  nitrification  of  the  Cyanamid 
is  complete  in  twenty  days.  Larger  applications  require  a 
longer  period,  but  are  of  no  practical  interest.  The  above 
results  must  be  considered  relatively  to  each  other  and  not  as 
absolute  values,  since  the  conditions  were  probably  very  favor- 
able to  nitrification. 

A  similar  experiment  is  reported  by  Muntz  and  Nottin.^ 
They  found  that  when  0.25  grams  of  nitrogen  per  kilogram  of 
soil  was  used,  the  relative  amount  of  nitrification  in  5  months 
for  different  fertilizers  was  as  follows : 

Per  cent. 

Ammonium  sulphate 100 

Calcium  cyanamide 88 

Dried  blood 66 

Roasted  leather 26 

The  above  fertilization  is  equivalent  to  about  450  pounds  of 
nitrogen  per  acre,  and  has  no  significance  to  practical  agricul- 
ture. 

When,  however,  smaller  amounts  of  Cyanamid  were  applied, 
nitrification  was  very  rapid,  and  further,  the  bacteria  rapidly 
adjusted  themselves  to  the  changed  environment  and  enorm- 
ously increased  their  ability  to  nitrify  Cyanamid  nitrogen,  even 
when  successively  increasing  doses  were  applied.  This  is 
shown  in  the  following  table : 

Amount  cyanamid  Amount 

nitrogen  applied  nitrogen  present  Nitrate  nitrogen 

each  time  at  analysis  before  per  kg.  of  earth 

Date  applied  grams  new  application  by  analysis 

January  17 0.06  —  — 

January  26 0.06  0.06  — 

February  7 o.io  0.12  o.oi 

March  3 0.12  0.22  0.18 

April  2 0.22  0.34  0.37 

April  25 ^.  0.40  0.56  0.58 

May  23 —  0.96  0.81 

*  Annales  de  I'lnstitut  National  Agronomique,  2nd  Series,  Vol.  VI, 
No.  I,  1907. 


64         CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES 

The  rate  of  nitrification  of  Cyanamid  is  somewhat  less  than 
that  of  sulphate  of  ammonia  when  both  are  applied  in  large 
doses.  In  doses  such  as  would  be  used  in  practical  agriculture 
there  is  probably  not  much  difference.  The  rate  of  nitrification 
must  vary  greatly  in  different  soils  and  individual  experiments 
can  show  but  little  of  general  application.  As  a  general 
average  of  observations  made  in  Germany,  it  appears  that  the 
duration  of  Cyanamid  nitrogen  in  the  soil  is  about  70-80  days. 
In  very  active  soils  it  is  probably  less,  in  cold  soils  of  low 
bacterial  activity  it  is  probably  more.  Its  duration  is  there- 
fore about  midway  between  that  of  ammonium  sulphate  and 
dried  blood. 


CHAPTER  VIII. 


Toxicity  of  Fertilizers, 


A  review  of  the  numerous  agricultural  experiments  that 
have  been  reported  since  1902,  indicates  that  Cyanamid  is  not 
equally  efficient  as  a  fertilizer  in  all  the  conditions  in  which  it 
has  been  applied.  Cases  have  been  noted  where  there  was  ap- 
parently an  unfavorable  action  on  germination  of  seeds,  unless 
the  fertilizer  were  mixed  with  the  soil  several  days  before  the 
seed  was  sown.  It  is  also  said  to  be  poorly  adapted  for  use  on 
acid  moor  soils  or  on  very  poor  sand  soils  of  low  activity. 
Various  explanations  have  been  given  of  the  cause  of  these 
undesirable  effects.  In  some  cases  the  occasional  harmful 
action  on  germination  has  been  attributed  to  the  evolution  of 
acetylene  from  a  crude  lime-nitrogen  containing  free  calcium 
carbide;  in  other  cases  the  causticity  of  the  lime  has  been 
blamed,  but  usually  the  unfavorable  action  on  acid  moor  soils 
or  very  poor  sand  soils  is  charged  to  the  formation  of  dicyan- 
diamide  by  the  acids  in  such  soils. 

Meaning  of  "Poison." — It  is  well  to  agree  at  once  upon  what 
is  meant  by  the  term  "toxin"  or  "poison."  Dr.  Paul  Wagner^ 
says  "poison,  as  is  known,  is  a  very  relative  idea,  for  poisons 
in  great  dilution  are  harmless,  and  non-poisons  in  great  con- 
centrations are  harmful."  It  is  obvious  that  the  term  "poison" 
could  be  applied  to  almost  any  substance  if  we  do  not  limit  the 
amount  which  is  understood  to  be  used.  Unless,  therefore,  the 
amount  which  is  said  to  be  toxic  is  distinctly  specified,  it  is 
necessary  to  assume  that  the  amount  used  is  small  and 
popularly  regarded  as  a  safe  dose.  It  is  also  desirable  to  agree 
upon  the  amount  of  injury  that  can  be  sustained  before  the 
effect  can  be  pronounced  as  harmful.  Some  substances  produce 
temporary  exhilaration,  followed  by  serious  depression;  other 
substances  produce  temporary  depression,  but  leave  the  subject 
^  Arbeit,  der  Deut.  Landw.  Ges.,  No.  129,  p.  267,  1907. 


66         CYANAMID — manufacture:,    CHEMISTRY   AND    USES 

in  the  long  run  better  than  before.  Practically,  from  the  stand- 
point of  plant  physiology,  it  seems  necessary  to  define  a  poison 
as  a  substance  which,  administered  in  quantities  ordinarily  con- 
sidered small,  produces  functional  disturbances  ending  ulti- 
mately in  permanent  injury  or  death.^ 

In  this  connection  it  may  be  well  to  quote  entire  the  con- 
clusions of  Dr.  Paul  Wagner  after  seven  years  of  experi- 
menting with  lime-nitrogen,  both  in  pot  cultures  and  in  the 
field.2 

CONCLUSIONS  OF  DR.  PAUL  WAGNER. 

"i.  The  statement  'lime  nitrogen  is  a  plant  poison  and  must 
be  converted  by  soil  bacteria  into  ammonia  and  nitric  acid  in 
order  to  act  as  a  fertilizer'  has  led  to  many  faulty  conceptions 
and  is  practically  not  correct.  Poison,  as  is  known,  is  a  very 
relative  term,  for  poisons  in  great  dilution  are  unharmful,  and 
non-poisons  in  great  concentration  are  harmful.  For  instance, 
perchlorate  occurring  in  nitrate  of  soda  is  a  decided  poison. 
If  one  sows  3  kg  of  perchlorate  on  a  hectare  of  rye, 
there  will  be  a  poisonous  action.  Chile  saltpeter  should 
therefore  contain  not  more  than  one-tenth  of  a  per 
cent,  of  perchlorate;  it  should  be  rejected  if  it  con- 
tains more  than  i  per  cent,  of  this  poison.  Likewise, 
ammonium  sulphocyanate  is  a  real  plant  poison.  In  the  year 
1873,  in  No.  38  of  the  Hessian  Agricultural  Journal,  I  com- 
municated a  marked  example  of  sulphocyanate  poisoning.  On 
the  Rudigheimer  estate  at  Hanau  a  grain  field  of  4  hectares 
was  poisoned  by  an  application  of  100  kilograms  of  ammonium 
superphosphate  with  10  per  cent,  nitrogen,  which  later  in- 
vestigation showed  to  contain  sulphocyanate.  Therefore,  this 
extremely  slight  amount  of  sulphocyanate  was  sufficient  to 
cause  a  characteristic  poisoning  and  to  decrease  the  yield  to 
about  one-third.  It  has  also  been  learned  that  ammonium 
sulphocyanate  applied  a  greater  or  less  time  before  sowing  of 

»  See  also  Pfeffer's  Physiology  of  Plants,  Ewart,  Vol.  II,  258. 

'  Arbeit.  Deut.  Landw.  Ges.,  Heft  129,  1907,  p.  267. 


CYANAMID — MANUI^ACTURE,    CHE:MISTRY    AND    USIiS         6/ 

the  seed,  can  under  certain  conditions  be  decomposed  into 
ammonia,  so  that  is  no  longer  poisonous.  Nevertheless,  the 
sulphocyanates  to  the  extent  that  they  remain  undecomposed 
in  the  soil  are  decided  plant  poisons  and  cannot  be  applied  as 
fertilizers. 

"On  the  contrary,  nitrate  of  soda,  sulphate  of  ammonia, 
nitrate  of  ammonia,  and  carbonate  of  ammonia  contained  in 
manure,  are  known  as  very  favorable  nitrogen  fertilizers  and 
they  are  still  regarded  as  such,  although  it  is  known  that  under 
certain  conditions  they  can  act  disadvantageous^.  Very  con- 
centrated solutions  of  these  nitrogen  fertilizers,  especially  car- 
bonate of  ammonia,  can,  as  is  evident  from  our  contribution  in 
Volume  66  of  the  Agricultural  Experiment  Station  Reports, 
have  a  depressing  action  upon  the  development  of  plants,  and 
under  certain  circumstances  (which  indeed  do  not  occur  in 
agricultural  practise)  they  can  produce  complete  destruction 
of  the  plant.  No  one,  however,  designates  nitrate  of  soda, 
sulphate  of  ammonia  or  manure  as  plant  poisons.  In  a 
similar  manner  it  is  known  that  fertilization  with  quicklime 
must  be  carried  out  with  great  care.  Professor  Tacke  has 
determined  by  researches  upon  moor  soils  a  very  disadvan- 
tageous action  of  lime  fertilization,  and  I,  and  others,  have 
found  that  lime  can  act  harmfully  on  ordinary  soils  if  the  lime 
is  applied  in  too  large  quantities  or  at  the  wrong  time.  No 
one  will,  however  call  quicklime,  which  is  known  as  a  highly 
valuable  fertilizer  material,  a  plant  poison. 

"In  just  the  same  way  Cyanamid,  or  so-called  lime 
nitrogen,  is  to  be  regarded  not  as  a  plant  poison,  but  as  a  fer- 
tilizer, although  it,  exactly  like  quicklime  and  other  fertilizers 
under  some  conditions,  can  act  harmfully  upon  the  growth  of 
plants.  Cyanides,  sulphocyanates  and  similar  nitrogen  com- 
pounds are  plant  poisons;  they  act  poisonously  in  very  great 
dilution  and  cannot  sa-ve  as  fertilizers  under  any  conditions. 
Cyanamid,  however,  does  not  belong  to  this  class,  for 
this  compound  can  act  harmfully  or  poisonously  upon  plants 
only  in  case  of  very  wrong  methods  of  application. 


68         CYANAMID — MANUFACTURie,    CHEMISTRY    AND    USES 

"When  Prof.  Frank  requested  me  six  years  ago  to  test 
Cyanamid  as  to  the  conditions  under  which  it  could  be 
used  as  a  fertilizer  and  its  relative  fertilizing  value,  I  had 
already  been  preparing  to  undertake  the  test;  but  I  had  ex- 
pected, on  the  ground  of  observations  made  with  cyanides  and 
sulphocyanates,  a  completely  negative  result  from  the  experi- 
ments. 

"Our  experiments  carried  out  in  the  laboratory  and  on  small 
experimental  plots  have  not  confirmed  my  previous  assump- 
tion. Our  field  experiments  have  shown  that  the  application 
of  lime  nitrogen  as  a  fertilizer  was  attended  with  less 
difficulties  than  one  could  directly  conclude  from  the  experi- 
ments carried  out  in  the  laboratory  and  on  small  experimental 
plots.  Very  concentrated  solutions  of  lime  nitrogen  or  ex- 
ceptionally large  applications  of  this  fertilizer  act  harmfully 
upon  the  plants,  as  is  clearly  seen  from  our  pot  experiments 
(see  page  71  and  Fig.  5).  Under  the  normal  conditions  of 
agricultural  practice,  however,  a  disadvantageous  action  does 
not  occur,  if  one  follows  the  directions  given  for  the  applica- 
tion of  Cyanamid,  and  these  consist  essentially  in  this  that  the 
lime  nitrogen  must  not  be  applied  in  excessive  quantities  and 
further  must  not  be  applied  upon  acid  soils  or  soils  which  tend 
to  become  acid;  that  it  must  be  distributed  as  uniformly  as 
possible  upon  the  surface  of  the  field,  and  must  then  be  worked 
into  the  ground,  when  it  is  not  used  as  a  top  dresser,  by  deep 
acting  tools,  or  be  plowed  under. 

"To  illustrate,  it  should  be  noted  that  in  our  experiments 
(see  page  71)  an  application  of  i  gram  of  nitrogen  in  the  form 
of  lime-nitrogen  upon  7  kilograms  of  soil  contained  in  a 
vessel  20  cm.  in  diameter  did  not  act  harmfully,  but  acted 
favorably  from  the  beginning  to  the  end  upon  the  plant  growth 
even  when  the  lime  nitrogen  was  mixed  with  the  soil  im- 
mediately before  planting  of  the  seed.  Upon  a  circumference 
of  20  cm.  diameter,  however,  one  does  not  apply  in  agricultural 
practice  i  gram,  but  only  one-tenth  or  at  the  highest  two-tenths 
of  a  gram  of  nitrogen.     It  is  therefore  clear  that  one  can 


CYANAMID — manufacture:,    CHEMISTRY    AND    USDS         69 


55 


I 


K 


r^wrf^By  u/&^B  ^o  p/9fi 


yO         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

regard  the  disadvantageous  action  of  lime  nitrogen,  such  as 
happens  under  applications  of  exceptionally  large  quantities  in 
pot  experiments  as  either  not  occurring  in  agricultural  practice 
or  as  immediately  disappearing.  Practically,  one  cannot  there- 
fore regard  lime  nitrogen  as  a  plant  poison.  It  is  to  be 
regarded  as  a  fertilizer  applicable  in  agricultural  practice  and 
having  a  favorable  action,  although  as  is  necessary  with  barn 
manure,  green  fertilizers,  bone-meal,  horn  meal,  etc.,  the  nitro- 
gen contained  in  it  must  be  converted  by  bacterial  activity  into 
ammonia  and  nitric  acid  in  order  that  it  may  serve  as  plant 
food. 

"2.  If  lime  nitrogen  is  applied  in  normal  quantities,  as  com- 
pared with  other  fertilizer  materials,  distributed  as  uniformly 
as  possible  upon  the  soil,  and  worked  in  well  with  deep-acting 
tools,  it  exerts  no  harmful  influence  even  when  applied  im- 
mediately before  sowing  of  the  seed.  The  idea  that  lime- 
nitrogen  must  be  completely,  or  at  least  to  a  great  extent, 
converted  into  ammonia  or  nitric  acid  before  it  comes  into  con- 
tact with  the  seed  is  wrong,  although  it  is  possible  that  the  action 
of  lime  nitrogen  in  many  cases  can  be  increased  if  it  is  applied 
8  or  14  days  before  sowing  of  the  seed. 

''3.  Lime  nitrogen  in  ordinary  field  practice  can  act  harm- 
fully only  when  conditions  are  such  that  a  part  of  the  calcium 
cyanamide  suffers  an  unnormal  decomposition.  Conditions 
under  which  this  can  happen  are  present  especially  in  acid  moor 
soils  or  in  soils  which  tend  to  become  acid,  or  soils  very  rich  in 
humus,  and  therefore  very  poor  in  lime.  It  is  known  that 
moor  soils  acts  otherwise  than  normal  towards  other  nitrogen 
fertilizers  as  well.  Sulphate  of  ammonia  has  an  unfavorable 
action  upon  acid  soils.  In  order  to  avoid  these  unfavorable 
conditions  of  acid  soils  previous  liming  is  necessary. 

"4.  Like  all  organic  nitrogen  fertilizers,  green  substances, 
barn  manure,  horn  meal,  etc.,  the  conversion  into  ammonia  and 
nitric  acid  is  necessary  in  order  to  yield  nitrogen  assimilable 
by  plants,  and  like  ammonia  (although  many  plants  take  it  up 
and  use  it  as  such),  for  most  plants  it  has  its  full  effect  only 


CYANAMID manufacture:,    CHEMISTRY    AND   USES         7I 

when  it  is  converted  into  nitric  acid;  so  the  nitrogen  of  the 
lime-nitrogen  must  be  converted  into  ammonia  and  nitric 
acid  Before  it  will  yield  nitrogen  that  the  plants  can  assimilate. 
"5.  It  is  known  that  the  conversion  of  Cyanamid  and  the 
organic  forms  of  nitrogen  into  ammonia  and  nitric  acid  is 
brought  about  by  the  activity  of  certain  soil  bacteria  and  that 
this  conversion,  according  to  the  special  activity  of  the  soil, 
sometimes  proceeds  more  rapidly  and  sometimes  more  slowly. 
Upon  so-called  medium  soils  in  good  condition  the  organic 
fertilizers  as  a  rule  act  more  completely  than  upon  light  dry 
sandy  soils  or  upon  heavy  clay  soils.  The  medium  loam  soils 
in  good  condition  seem  to  offer  comparatively  the  best  con- 
ditions for  the  action  of  lime  nitrogen.  Whether  the  con- 
version of  calcium  cyanamide  into  ammonia  proceeds  by  an 
intermediate  formation  of  urea  is  unproved." 

The  above  was  written  by  Dr.  Wagner  before  the  mechanism 
of  the  conversion  of  Cyanamid  in  the  soil  had  been  worked 
out.  These  later  researches  show  that  the  conversion  is  both 
physico-chemical  and  biological,  as  has  been  set  forth  in 
Chapter  V. 

The  experiments  on  the  effect  of  concentration  to  which 
Dr.  Wagner  refers  were  made  in  vegetation  pots  with  a 
variety  of  nitrogenous  compounds,  on  various  types  of  soil, 
and  with  various  crops.  All  the  results  point  to  the  same 
general  conclusion,  which  is  illustrated  in  Fig.  5.  This  test 
was  made  with  oats  planted  on  a  sandy-loam  soil,  in  pots 
20  cm.  high  and  20  cm.  in  diameter.  The  seed  was  planted 
on  the  day  of  fertilizing.  May  9,  1905,  and  the  grain  harvested 
on  July  14,  1905.  The  lime-nitrogen  contained  20.06  per  cent, 
nitrogen,  and  the  calcium  nitrate  (commercial  grade)  con- 
tained 11.65  P^^*  cent,  nitrogen.^  The  yields  of  grain  are 
plotted  against  the  amounts  of  nitrogen  applied  to  the  soil 
(Fig.  5)- 

Each   of   these   curves    is   an   illustration   of   the   Law   of 
Diminishing  Returns.     For  the  smaller  applications  of  nitro- 
1  Landw.  Vers.  Stat.,  66,  IV-V  (1907),  p.  346. 
6 


y2         CYANAMID — MANUFACTURE^    CHEMISTRY    AND    USES 

gen,  the  increased  yield  is  almost  proportional  to  the  amount 
of  nitrogen  applied,  but  the  rate  of  increase  drops  off  rapidly 
until  a  point  is  reached  where  further  applications  not  only 
do  not  increase  the  yield  but  tend  to  decrease  it.  If  too  much 
fertilizer  is  applied  the  plant  may  even  be  killed.  The  "burn- 
ing" and  occasional  destruction  of  vegetation  by  excessive 
applications  of  fertilizer  salts  is  well  known  to  agriculturists. 
A  similar  phenomenon  has  been  investigated  by  Headden  and 
Sackett^  in  Colorado,  where  it  was  shown  that  the  formation 
of  excessive  quantities  of  nitrates  has  caused  in  some  cases 
the  total  destruction  of  all  plant  life,  often  over  areas  miles 
in  extent. 

Toxicity,  therefore,  is  a  question  of  the  amount  of  fertilizer 
applied.  All  of  the  common,  nitrogenous,  mineral  fertilizers 
may  have  a  toxic  action  if  too  much  is  used,  but  with  the 
ordinary  applications  of  practical  agriculture  none  of  these 
materials  is  toxic.  Experience  has  determined  the  maximum 
quantities  of  nitrogen  that  can  be  economically  utilized  by  the 
various  crops  under  various  soil  conditions,  and  the  possible 
effects  of  larger  quantities  than  this  maximum  economical 
quantity  in  each  case  have  little  interest  to  the  practical  farmer. 
Cotton,  corn,  wheat,  oats,  and  similar  crops  seldom  economically 
utilize  more  than  15  to  25  pounds  of  nitrogen  per  acre.  Sugar 
beets  and  sugar  cane  may  utilize  as  high  as  40  to  50  pounds. 
Potatoes,  truck  crops,  some  fruits,  and  tobacco  may  utilize  as 
high  as  60  to  70  pounds  of  nitrogen  per  acre.  With  such 
applications  it  is  doubtful  if  any  of  the  mineral  fertilizers  in 
question  would  exert  a  toxic  action  on  the  plant,  even  if  they 
were  applied  alone,  provided  the  time  and  method  of  applica- 
tion were  suitable. 

As  a  matter  of  fact,  however,  when  large  applications  of 

nitrogen  are  desired,  it  is  customary  to  mix  several  kinds  of 

nitrogenous  materials  together  and  to  apply  the  mixture  in 

several  portions,  instead  of  all  at  one  time.     Moreover,  agri- 

^  Colorado  Exp.  Sta.  Bulletin  179,  191 1. 


CYANAMID — manufacture:,    CHEJMISTRY    AND    USES         73 

cultural  experience  has  shown  that  nitrogenous  fertilizers  are 
not  utilized  as  economically  when  applied  alone  as  when  they 
are  used  in  conjunction  with  phosphates  and  potash  salts;  the 
presence  of  phosphorus  and  potassium  seems  to  greatly  modify 
the  ability  of  the  plant  to  assimilate  nitrogen.  As  a  general 
rule,  it  is  seldom,  indeed,  that  more  than  25  pounds  of  nitro- 
gen, derived  from  a  single  source,  is  applied  at  one  time, 
unaccompanied  by  phosphates  and  potash.  In  normal  agri- 
cultural practice,  therefore,  the  question  of  toxicity  of  the 
common  nitrogenous  fertilizers  may  be  disregarded.  If  the 
farmer  wishes  to  depart  from  the  normal  practice,  it  is  usually 
best  to  follow  the  instructions  issued  by  fertilizer  manufac- 
turers for  the  use  of  their  products.  Such  instructions  usually 
designate  20  to  25  pounds  of  nitrogen  per  acre  as  the  maximum 
application,  and  recommend  that  the  material  be  applied  during 
the  preparation  of  the  soil  a  week  or  more  before  the  seed 
is  sown.  They  also  caution  against  the  danger  of  direct 
contact  of  the  undiluted  fertilizer  with  the  leaves  or  roots  of 
the  plant. 

OTHER  EXPLANATIONS  OF  TOXIC  ACTION. 

Whether  or  not  acetylene,  which  may  be  generated  by  the 
action  of  moisture  on  a  lime-nitrogen  containing  calcium  car- 
bide, is  harmful  to  plant  life,  is  of  little  interest  to  the 
Cyanamid  industry,  since  the  material  prepared  for  use  as  a 
fertilizer  does  not  contain  calcium  carbide.  The  lime-nitrogen 
made  in  Europe  in  former  years,  sometimes  contained  slight 
amounts  of  carbide  but  it  is  extremely  doubtful  if  there  were 
any  harmful  effects  from  this  ingredient.  H.  Kappen^  and 
E.  Haselhoff^  claim  that  they^  could  observe  no  harmful  effects 
of  acetylene  on  plant  growth.  No  reports  have  been  found 
which  show  that  acetylene  may  be  harmful. 

The  free  lime  in  the  German  "kalkstickstoff"  or  lime- 
nitrogen  is  in  the  form  of  calcium  oxide,  while  in  the  Ameri- 

^  Fuhling's  Landw.  Zeit.,  Apr.  1908,  286. 
»  Landw.  Vers,  stat.,  68,  1908,  Nos.  3  and  4. 


74      CYANAMiD — manufacture;,  che:mistry  and  use:s 

can  Cyanamid  it  is  in  the  form  of  calcium  hydroxide  and 
carbonate.  The  effects  of  the  lime  in  either  form  upon  plant 
life  have  been  stated  clearly  by  Wagner  in  the  extract  quoted 
above.  Since  the  amount  of  total  calcium  in  Cyanamid,  ex- 
pressed as  CaO  is  about  55  per  cent,  and  the  amount  applied 
to  the  soil  is  necessarily  limited  by  the  amount  of  nitrogen 
applied,  the  lime  can  hardly  reach  such  an  amount  that  it 
will  ever  interfere  with  plant  growth. 

With  regard  to  the  inferior  action  of  Cyanamid  on  acid 
moor  soils,  or  on  other  acid  soils,  Wagner  states  that  the  same 
thing  is  true  of  ammonium  sulphate,  and  that  the  bad  effects 
should  be  attributed  to  the  abnormal  soil  conditions  and  not 
to  any  abnormal  action  of  the  fertilizer.  Soils  which  are  acid 
are  as  a  rule  unfit  for  profitable  agriculture,  and  should  be 
put  into  good  condition  by  previous  judicious  liming.  Fer- 
tilizers cannot  be  expected  to  overcome  the  harmful  effects  of 
abnormal  conditions  which  constitute  the  limiting  factor  in 
the  growth  of  a  crop.  The  abnormal  conditions  must  be  cor- 
rected before  fertilization  will  be  most  economical.  Cyanamid, 
therefore,  should  not  be  applied  to  very  acid  soils  with  the 
expectation  of  obtaining  a  profit,  unless  the  unfavorable  con- 
ditions are  corrected  by  previous  liming.  The  quantity  of 
lime  in  Cyanamid,  while  of  some  assistance,  is  evidently  insuffi- 
cient on  very  acid  soils,  which  require  frequently  as  much 
as  one  to  two  tons  of  slaked  lime  in  order  to  restore  them  to 
a  neutral  reaction. 

The  unfavorable  action  of  Cyanamid  on  very  acid  soils  has 
frequently  been  attributed  to  the  possible  formation  of  dicyan- 
diamide  from  the  calcium  cyanamide.  That  there  is  no  chem- 
ical or  experimental  basis  for  this  explanation  will  be  shown 
in  the  next  section. 

DICYANDIAMIDE. 

The  subject  of  dicyandiamide  has  been  much  discussed  in 
chemical  literature.  It  has  been  necessary,  in  order  to  gain 
a  logical  understanding  of  the  subject,  to  select  from  the  mass 


CYANAMID MANUFACTURE,    CHEMISTRY   AND    USES         75 

of  experimental  data  that  have  been  reported  the  results  that 
are  consistent  with  all  the  known  facts,  and  then  to  reconcile 
the  apparent  disagreements  with  the  consistent  facts. 

Formation. — The  researches  of  Ulpiani^  show  without  doubt 
that  acids  do  not  determine  the  formation  of  dicyandiamide 
from  calcium  cyanamide.  Acids  acting  on  calcium  cyana- 
mide  produce  calcium  salts  and  free  cyanamide.  By  the 
further  action  of  the  acids,  from  the  weakest  to  the  strongest, 
there  is  formed  first  urea,  and  secondly,  especially  in  the  case 
of  weak  acids,  ammonium  salts.  (See  also  p.  12).  F. 
Lohnis  and  R.  MolP  found  that  even  humic  acid,  in  excess, 
acting  upon  lime-nitrogen  for  8  days  at  40°  C.  produced  not 
the  slightest  trace  of  dicyandiamide.  There  is  no  evidence  of 
any  kind  to  show  that  acids  ever  produce  dicyandiamide  from 
cyanamide.  Neither  do  strong  alkalies  produce  dicyandiamide, 
but  always  produce  urea  and  free  ammonia.  Weak  alkalies, 
however,  and  especially  calcium  hydroxide,  readily  effect  the 
polymerization,  although  in  this  case  also  there  is  formed  con- 
siderable urea.  The  formation  of  dicyandiamide  in  lime- 
nitrogen  is  brought  about  by  the  combined  action  of  moisture, 
which  causes  the  hydrolysis  of  calcium  cyanamide  to  cyan- 
amide, and  lime  which  determines  its  polymerization  to  dicyan- 
diamide. These  reactions  take  place  at  ordinary  temperatures 
very  slowly,  as  shown  below,  but  proceed  very  rapidly  above 
70°  C.  At  about  100°  C.  other  reactions  begin  with  formation 
of  ammonia  and  small  amounts  of  other  derivatives.  Water 
and  heat  alone  do  not  cause  the  polymerization  to  dicyandi- 
amide; Ulpiani  boiled  a  pure  solution  of  cyanamide  50  hours 
without  any  change.^ 

Decomposition. — In  a  solution  of  lime-nitrogen,  dicyan- 
diamide forms  and  decomposes  simultaneously.    This  is  seen 

• 
^  Gaz.  Chim.  Ital.,  1908,  II,  No.  4,  358.417. 

»  Centl.  Bakt.  XXII,  276. 

^  Rend.  Soc.  China,  di  Roma.  p.  4  1906. 


^J^y         CYANAMID — MANU]?ACTURE,    CHE:MISTRY   AND    USES 

in  the  following  table  by  G.  Liberi,^  showing  the  content  of 
cyanamide  and  dicyandiamide  nitrogen  in  solutions  of  lime- 
nitrogen  made  by  extracting  with  cold  water  and  filtering  and 
maintaining  at  27°  C.  The  figures  are  given  as  percentages 
of  the  original  lime-nitrogen. 


Dilute  solution  i  per  cent,  lime 
nitrogen 

Concentrated  solution  5  per  cent, 
lime  nitrogen 

'ime  elapsed 
in  days 

Nitrogen  as 
cyanamide 
per  cent. 

Nitrogen  as 

dicyandiamide 

percent. 

Nitrogen  as 

cyanamide 

per  cent. 

Nitrogen  as 

dicyandiamide 

per  cent. 

0 

18.63 

-- 

18.63 

— 

I 

16.38 

0.46 

14.56 

0.70 

2 

14.42 

0.56 

11.76 

1.54 

6 

12.74 

0.62 

9.10 

2.84 

II 

10.22 

0.50 

5.18 

2.24 

18 

7.42 

0-39 

1-75 

I.71 

31 

3.01 

0.38 

0.00 

1.25 

45 

0.00 

0.34 

— 

0.84 

58 

— 

0.28 

— 

0.53 

76 

— 

0.22 

— 

0.23 

The  maximum  amount  of  dicyandiamide  occurs  in  each  case 
at  the  end  of  6  days'  standing.  The  decomposition  of  the 
dicyandiamide  is  very  slow,  as  is  seen  in  the  concentrated 
solution  after  the  31st  day,  when  all  the  Cyanamid  has  been 
removed,  and  no  more  dicyandiamide  can  form.  Its  rate  of 
formation  is  somewhat  faster,  and  is  undoubtedly  determined 
by  the  concentration  of  both  nitrogen  and  calcium.  The  per- 
centage of  the  total  nitrogen  transformed  to  dicyandiamide 
is  about  five  times  as  great  in  the  concentrated  as  in  the  dilute 
solution.  With  the  removal  of  the  cyanamide  it  was  observed 
that  crystals  of  pure  calcium  hydroxide  settled  out  on  the 
walls  of  the  vessel. 

The  rapid  disappearance  of  the  cyanamide  shows  that  the 
formation  of  other  derivatives  of  cyanamide  in  this  solution  is 
much  more  rapid  than  the  formation  and  decomposition  of 
dicyandiamide,  and  it  is  therefore  evident  that  most  of  the 
cyanamide  decomposes  directly  to  these  other  derivatives,  and 
not  through  the  dicyandiamide  form.  The  largest  part  of 
^  Annali  Staz  Chim.  Agrar.  Sper  di  Roma  Series  II,  V,  1911. 


CYANAMID — manufacture:,    CHEMISTRY    AND    USES         ^J 

these  other  derivatives  is  urea,  and  the  balance  is  amidodi- 
cyanic  acid,  melamine  and  ammeline.     (See  also  p.  29). 

Conversion  in  Soil. — The  chemical  behavior  of  dicyandiamide 
in  the  soil  has  not  been  studied  in  the  thorough  manner  in 
which  that  of  cyanamide  has  been  studied,  and  much  of  the 
data  at  hand  is  invalidated  by  the  fact  that  enormous  quanti- 
ties of  nitrogen  were  used.  It  is  necessary  to  draw  our  con- 
clusions solely  from  the  vegetation  tests  that  have  been 
reported. 

A  review  of  these  culture  tests  will  show  that  they  fall  into 
two  classes ;  one,  in  which  chemically  pure  dicyandiamide  was 
used,  and  the  other  in  which  home-made  dicyandiamide  was 
used. 

Among  the  prominent  investigators  who  used  pure  dicyan- 
diamide are  Wagner,  Kappen,  Sabaschinkofif,  Lohnis,  Brioux, 
and  C.  J.  Milo.  Their  results  show  that  chemically  pure 
dicyandiamide  has  practically  no  fertilizing  value  but 
on  the  other  hand  may  have  slight  toxic  action  if  more 
than  45  pounds  of  dicyandiamide  nitrogen  per  acre  is  applied. 
The  results  are  in  such  agreement  that  it  will  not  be  necessary 
to  quote  them  here.  Among  those  who  used  dicyandiamide 
prepared  in  their  own  laboratories  are  Perotti,  Ulpiani,  R. 
Inouye  and  K.  Aso.  They  found  that  home-made  dicyandia- 
mide has  a  fertilizing  value  equal  to  that  of  ammonium  sul- 
phate provided  it  is  not  used  in  quantities  exceeding  100 
pounds  of  nitrogen  per  acre. 

Perotti,^  for  instance,  in  pot  tests  with  wheat,  grown  to 
maturity,  obtained  the  maximum  crop  with  75  pounds  of  nitro- 
gen per  acre  i-n  the  form  of  home-made  dicyandiamide.  The 
increase  in  yield  over  the  control  pot  without  nitrogen  was 
about  100  per  cent.  With  buckwheat  the  maximum  crop  was 
obtained  with  150  pounds  of  nitrogen  per  acre,  and  the  in- 
crease in  yield  was  abojit  200  per  cent.  With  flax  the  maximum 
yield  was  with  300  pounds  of  nitrogen,  and  the  increase  in 
yield  was  about  60  per  cent. 
1  Cent.  Bakt.  XVIII,  55,  1907. 


78         CYANAMID — MANUI^ACTURE:,    CHEMISTRY    AND    USES 

R.  Inouye^  made  pot  tests  with  rape  and  barley,  fertilizing 
with  a  dicyandiamide  made  by  himself  from  lime-nitrogen,  and 
and  analyzing  46.7  per  cent,  nitrogen.  The  rate  of  fertiliza- 
tion was  equivalent  to  2,400  pounds  superphosphate  per  acre, 
1,200  pounds  potassium  carbonate  and  the  amounts  of  nitrogen 
shown  in  the  table  below,  which  gives  also  the  yield  obtained : 


Pounds  nitrogen 

from 
ammon.  sulphate 

Pounds  nitrogen 

from 
dicyandiamide 

Average  weight 

of  one  plant 

green  rape.  Grams 

Average  weight 

of  one  plant 

air-dry,  barley.  Grams 

— 

— 

5.0 

1.8 

240 
160 

80 

59.4 
62.6 

8.3 
9.0 

160 

80 

64.0 

9.0 

— 

240 

8.4 

2.5 

The  dicyandiamide  in  the  fourth  pot  was  applied  as  a  top- 
dressing.  Although  the  fertilization  was  very  heavy  there  is 
no  doubt  that  the  results  are  very  good  when  80  pounds  of 
nitrogen  from  impure  dicyandiamide  is  used  with  ammonium 
sulphate,  although  240  pounds  of  nitrogen  from  dicyandiamide 
alone  is  little  better  than  no  fertilizer.  This  is  clearly  an  ex- 
cessive amount  of  dicyandiamide. 

K.  Aso^  made  some  toxicity  tests  with  a  dicyandiamide 
made  by  himself  from  lime-nitrogen,  and  analyzing  59.88  per 
cent,  nitrogen.  Buckwheat  and  oat  plants  were  grown  to  a 
height  of  about  10  cm.  in  ordinary  soil  and  were  then  trans- 
ferred to  flasks  containing  solutions  of  different  concentrations 
of  dicyandiamide.  When  the  solutions  contained  less  than 
o.oi  per  cent,  of  nitrogen  from  dicyandiamide  the  plants  con- 
tinued growing  normally  and  developed  better  than  in  the 
control  flasks.  When  larger  concentrations  were  used  the 
plants  showed  the  characteristic  effects  of  dicyandiamide 
poisoning;  that  is,  for  increasing  doses,  first,  appearance  of  a 
brown  color  on  the  tips  of  the  leaves,  then  drying  of  the  tips, 
although  usually  followed  by  recovery  and  increased  growth; 
finally,  with  very  large  concentrations,  curling  and  drying  up 
of  the  leaves  and  destruction  of  the  plant.     Here,  as  with 

1  Jour.  Coll.  Agr.  Imp.  Univ.  Tokyo,  Vol.  I,  No.  2,  1909,  p.  193. 

2  Jour.  Coll.  Agr.  Imp.  Uuiv.  Tokyo,  Vol.  i,  No.  2,  1909,  p.  211. 


CYANAMID — manufacture:,    CHEMISTRY    AND    USEJS         79 

Cyanamid  and  other  fertilizers,  toxicity  is  a  question  of  con- 
centration, although  the  specific  toxicity  of  pure  dicyandiamide 
is  considerably  larger  than  that  of  impure  dicyandiamide. 

Some  tests  were  also  made  with  rice  transplanted  to  field 
plots  (0.83  qm.)  manured  alike  with  superphosphate,  potassium 
carbonate  and  nitrogen  compounds  at  the  rate  of  90  pounds 
per  acre  each  of  phosphoric  anhydride,  potash  and  nitrogen 
(except  control).  The  nitrogenous  substances  were  am- 
monium sulphate  containing  21.2  per  cent,  nitrogen,  lime-nitro- 
gen with  12.47  P^i"  cent,  nitrogen,  and  dicyandiamide  with  46.7 
per  cent,  nitrogen.  They  were  applied  at  different  periods  be- 
fore the  transplanting  of  the  rice  clumps.  The  total  weight 
in  grams  of  the  plants  obtained  in  the  air  dried  state  were : 

Fertilized  days  before  planting 

Fertilized  with                     o  7  14             21  28  35 

No  manure 229  —  —  —  —  — 

No  nitrogen 436  —  —  —  —  — 

Ammonium  sulphate  •  •  764  —  —  —  —  — 

Lime-nitrogen 614  767  786  807  788  744 

Dicyandiamide   507  575  572  670  652  609 

The  yield  of  clean  grain  was  as  follows : 

Fertilized  days  before  planting 

Fertilized  with  0                 7  14  21  28  35 

No  manure 75  —  —  —  —  — 

No  nitrogen 149  —  —  —  —  — 

Ammonium  sulphate  •  •  266  —  —  —  —  — 

Ivime-nitrogen 197  259  260  258  280  257 

Dicyandiamide 183  208  209  238  244  239 

This  experiment  shows  a  somewhat  lower  result  with  lime- 
nitrogen  than  with  ammonium  sulphate  applied  at  the  time  of 
planting,  but  a  somewhat  larger  yield  when  the  lime-nitrogen  is 
applied  7  days  before  planting.  The  dicyandiamide  is  more 
effective  when  applied  two  or  three  weeks  before  planting  than 
when  applied  at  the  planting,  but  it  is  never  as  effective  as 
the  ammonium  sulphate,  being  at  the  best  about  89  per  cent, 
as  effective  in  producing  grain.  In  the  cultivation  of  rice  in 
America  the  maximum  utilizable  application  of  nitrogen  does 


8o         CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES 

not  exceed  lo  pounds  per  acre.     Hence,  the  above  quantities 
are  many  times  larger  than  any  met  in  agricultural  practice. 

A  similar  experiment  was  made  in  pots  containing  8  kg.  of 
soil,  manured  with  double  superphosphate,  potassium  sulphate 
and  nitrogen  at  the  rate  of  120  pounds  of  PoOj,  K2O  and  N  per 
acre  respectively.  The  lime-nitrogen  contained  11.8  per  cent. 
N  and  the  dicyandiamide  59.9  per  cent  .N.  The  yields  in  grams 
of  air-dry  plants  were  as  follows : 

Fertilized  days  before  planting 

Fertilized  with  o  7  14  21 

Ammonium  sulphate  .. .  67.5  —  —  — 

Lime-nitrogen 65.6  69.6  70.6  74.8 

Dicyandiamide    66.6  74.3  73.8  71.5 

The  yields  of  grain  were : 

Fertilized  days  before  planting 

Fertilized  with  o  7  14  21 

Ammonium  sulphate  •  • .  29.5  —  —  — 

Lime-nitrogen 28.3  30.0  29.5  33.2 

Dicyandiamide   30.5  33.5  31.7  33.7 

In  this  experiment  the  highest  results  were  obtained  with 
dicyandiamide  applied  a  week  before  planting.  When  applied 
at  the  time  of  planting  the  results  are  about  the  same  as  those 
with  ammonium  sulphate. 

PURE  SUBSTANCES  AND  TOXICITY. 

There  are  several  observations  reported  in  the  literature  that 
may  help  us  to  understand  why  a  chemically  pure  dicyandia- 
mide should  be  toxic,  while  an  impure  dicyandiamide  may  have 
a  fertilizing  value  equal  to  that  of  ammonium  sulphate. 

It  has  been  noted  by  Sabaschnikoff^  that  a  fertilization  with 
chemically  pure  calcium  cyanamide,  in  comparison  with  lime- 
nitrogen  containing  the  same  amount  of  nitrogen,  gives  only 
from  one-third  to  one-half  as  large  an  increase  in  yield  as  is 
obtained  from  the  lime-nitrogen,  both  being  applied  under 
exactly  the  same  conditions. 

C.  J.  Milo^  made  some  experiments  on  sugar  cane,  in  which 

1  Mitt.  Landw.  Inst.,  Univ.  Leipzig,  Vol.  IX  1908,  p.  106. 

2  Archief  voor  de  Suikerindustrie  in  Nederlandsch-Indie,  20,  482-539. 


CYANAMID — MANUIPACTURE,    CHEMISTRY   AND    USES         8l 

the  sugar  cane,  in  baskets,  was  watered  one  month  and  two 
months  respectively  after  planting,  with  solutions  of  lime- 
nitrogen  (6  per  cent,  calcium  carbide),  pure  cyanamide, 
CN.NH2,  basic  calcium  cyanamide,  urea  and  dicyandiamide. 
The  solutions  contained  each  an  amount  of  nitrogen  equivalent 
to  an  application  of  75  pounds  per  acre.  The  pure  cyanamide 
proved  very  toxic  and  two  out  of  three  plants  were  killed  after 
the  second  application.  About  two  weeks  after  the  second 
application,  probably  when  the  cyanamide  had  been  converted 
to  other  forms,  the  remaining  plants  in  this  basket  began  to 
grow  luxuriantly.  The  basic  calcium  cyanamide  caused  the 
plants  to  look  sick  temporarily,  and  they  remained  inferior. 
The  dicyandiamide  (98.5  per  cent,  pure)  was  not  as  intense 
in  its  action  as  pure  cyanamide,  causing  no  destruction,  but 
the  bad  effects  lasted  longer  than  those  of  pure  cyanamide,  and 
the  plant  seemed  to  lack  nitrogen  nourishment.  The  urea 
caused  luxuriant  growth  from  the  time  of  application,  and  was 
slightly  better  than  the  sulphate  of  ammonia  and  lime-nitrogen 
applications.  The  lime-nitrogen  and  sulphate  of  ammonia 
solutions  produced  full  growth  and  were  equally  effective. 

It  appears  therefore,  that  the  fertilizing  value  of  lime- 
nitrogen,  decidedly  can  not  he  judged  from  the  fertilising 
action  of  pure  cyanamide  or  pure  calcium  cyanamide,  and  that 
the  fertilizing  value  of  impure  dicyandiamide  is  quite  different 
from  the  fertilizing  value  of  pure  dicyandiamide.  It  seems 
that  the  plant  is  unable  to  utilize  these  pure  compounds  of 
nitrogen,  but  that  in  lime-nitrogen  there  are  some  substances 
that  neutralize  such  toxic  compounds,  or  help  remove  them,  or 
that  act  upon  the  plant  in  such  a  way  as  to  enable  it  to  with- 
stand the  toxic  properties  until  they  are  destroyed  by  the  con- 
version of  the  cyanamide  and  its  polymers  by  the  catalytic 
action  of  the  soil.  It  is  quite  possible  for  instance,  that  the 
lime  and  the  extremely  finely  divided  carbon  in  lime-nitrogen 
may  play  a  part  in  the  rapid  decomposition  of  the  cyanamide. 
It  is  also  possible  that  the  urea,  and  other  derivatives  that  are 
so   easily   formed    from   cyanamide,    furnish   the  plant   with 


82         CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USE:S 

nourishment  that  enables  it  to  withstand  otherwise  toxic  effects 
that  might  check  growth  if  such  nourishment  were  not  avail- 
able (see  also  page  34). 

Conclusion.— Toxicity  of  Cyanamid  is  simply  a  question  of 
concentration.  Under  normal  soil  conditions  and  with  the 
normal  applications  of  practical  agriculture  there  are  no  un- 
usual effects  on  the  germination  of  the  seed  or  on  the  growth 
of  the  plant.  This  is  verified  constantly  in  the  extensive  use 
of  Cyanamid  in  agriculture. 


CHAPTER  IX. 


Agricultural  Use  of  Cyanamid. 


Fertilizer  Tests. — In  the  selection  of  the  most  economical 
fertilizer  it  is  necessary  to  consider,  among  other  things,  the 
nature  of  the  crop,  the  qualities  desired  in  the  plant  grown, 
the  type  of  soil,  the  effect  of  long-continued  use  of  the  fer- 
tilizer, the  cost  and  the  relative  yields.  Thus,  the  rice-plant 
seems  to  be  unable  to  assimilate  nitrates  easily,  but  readily 
assimilates  ammonium  compounds.^  The  quickly  acting 
forms  of  nitrogen  usually  produce  rank,  heavy  growth 
of  the  green  parts  of  the  plant,  with  little  fiber,  while 
the  slowly  acting  forms  produce  thinner  leaves,  and  stems 
with  greater  strength.  For  forcing  purposes,  the  nitrates  are 
ideal ;  for  slow,  steady  growth,  the  organic  forms  of  nitrogen, 
Cyanamid,  ammonium  sulphate,  etc.,  are  to  be  preferred.  Soil 
conditions  are  often  a  determining  factor.  Thus,  loose,  open 
soils  in  regions  that  receive  a  great  deal  of  rain  do  not  readily 
retain  nitrates.  Soils  of  low  lime  content  may  become  acid 
by  the  addition  of  ammonium  sulphate  year  after  year:  the 
sulphate  radical  enters  into  combination  with  the  lime  of  the 
soil  and  carries  away  the  calcium  in  the  drainage  waters.^ 
Very  acid  soils  are  not  economically  fertilized  with  substances 
like  Cyanamid,  ammonium  sulphate  and  other  materials  requir- 
ing nitrification,  since  nitrifying  bacteria  are  notably  deficient 
in  acid  soils,  especially  acid  sandy  soils.  Such  soils  should  be 
put  into  productive  condition  by  proper  judicious  liming,  some 
time  previous  to  the  fertilization.  On  light,  sandy  soils  where 
heavy  liming  may  damage  the  crop  the  yearly  addition  of  a 
small  amount  of  lime  as  a  part  of  the  fertilizer  is  of  great 
assistance  in  overcoming  the  tendency  towards  acidity.  The 
relative  yields  per  unit  of  money  invested  in  the  different  fer- 
tilizers is  often  the  controlling  factor  in  their  selection,  but 

1  Hawaiian  Agr.  Exp.  Sta.  Bulletin  24. 

2  A.  D.  Hall,  Fertilizers  and  Manures,  p.  62,  1909. 


84         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USEJS 

since  prices  vary,  it  is  customary  to  express  the  yields  on 
the  basis  of  equal  applications  of  nitrogen. 

There  is  therefore  a  large  number  of  factors  that  affect  the 
selection  of  the  most  economical  fertilizers.  The  statistical 
method  of  merely  averaging  the  yields  of  a  large  number  of 
experiments  regardless  of  their  character,  does  not  give  very 
much  practical  information.  The  errors  of  experimentation 
with  Cyanamid  are  usually  in  one  direction,  and  hence  do 
not  offset  one  another.  One  of  the  most  common  errors  is 
the  use  of  quantities  of  nitrogen  far  in  excess  of  what  would 
be  applied  in  practical  agriculture,  as  indicated  on  page  69. 
It  is  shown  in  Fig.  5  that  the  relative  efficiency  of  utilization, 
of  the  nitrogen  in  various  compounds  is  not  the  same  at  all 
applications.  The  relative  values  at  an  application  of  i  gram 
per  pot  are  entirely  different  from  the  relative  values  at  0.5 
grams,  or  at  lower  applications.  Moreover,  the  order  of 
superiority  may  be  different  at  different  applications,  as  shown 
on  the  calcium  nitrate  curve.  At  the  lower  concentrations, 
such  as  obtain  in  practical  agriculture,  under  favorable 
soil  conditions,  all  of  the  common  nitrogenous  mineral 
fertilizers  have  about  the  same  efficiency  of  utilization, 
in  this  experiment.  Not  only  is  it  a  mistake  to  assume  that 
results  obtained  at  one  concentration  will  hold  true  for  other 
concentrations,  but  it  is,  of  course,  equally  wrong  to  assume 
that  an  average  of  the  results  at  various  concentrations  will 
hold  true  for  a  particular  concentration.  The  relative  effi- 
ciencies also  vary  with  the  nature  of  the  soil  and  with  the 
crop.  Results  obtained  on  sand  may  not  hold  on  clay,  and 
vice  versa.  Acid  soils  may  act  differently  from  neutral  or 
alkaline  soils.  A  nitrogenous  fertilizer  applied  alone  usually 
gives  entirely  different  results  when  mixed  with  other  nitro- 
genous fertilizers,  or  with  phosphates,  acid  or  basic,  or  with 
potash  salts. 

A  source  of  error  that  has  probably  vitiated  many  of  the 
reported  experiments  is  the  readiness  with  which  unhydrated 
lime-nitrogen  changes  in  weight,  by  absorption  of  moisture 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES         85 

and  carbon  dioxide,  especially  when  stored  in  small  quantities. 
It  is  possible  that  a  great  many  investigators  have  purchased 
lime-nitrogen  at  a  certain  analysis,  have  allowed  the  material 
to  remain  exposed  to  the  atmosphere  several  months,  and 
have  then  weighed  out  the  fertilizer  for  the  test,  assuming  that 
its  analysis  is  practically  the  same  as  when  it  was  bought. 
The  error  introduced  by  the  weighing  up  of  the  fertilizer  one 
month  after  analysis  may  amount  to  5  to  8  per  cent,  of  the 
total  nitrogen,  in  the  case  of  a  single  bag  exposed  in  a  damp 
climate.  In  America,  where  the  Cyanamid  is  completely 
hydrated,  the  error  is  much  less  (see  p.  27),  but  it  is 
still  large  enough  to  make  it  desirable  to  have  the  fer- 
tilizer weighed  out  shortly  after  the  analysis  is  determined. 

Another  error  is  the  application  of  Cyanamid  only  a  short 
time  before  the  harvest.  Since  Cyanamid  may  take  70  to  80 
days^  to  be  completely  utilized,  it  is  obvious  that  the  maximum 
efficiency  is  obtained  only  when  the  application  is  made  not 
less  than  70  to  80  days  before  the  harvest. 

The  main  purpose  of  a  fertilizer  test  is  to  determine  the  rela- 
tive profits  that  can  be  made  by  the  use  of  different  fertilizers. 
In  view  of  the  difficulties  of  experimentation,  and  the  danger 
of  drawing  unwarranted  conclusions  from  insufficient  or 
irrelavant  data,  as  pointed  out  above,  probably  the  only  fair 
test  of  a  fertilizer  is  obtained  when  it  is  applied  under  the  con- 
ditions that  prevail  where  the  consumer  uses  it.  All  other 
methods  require  special  proof  that  the  results  obtained  experi- 
mentally would  also  be  obtained  practically,  and  such  proof 
is  not  always  available. 

To  illustrate  the  considerable  variation  in  the  results 
obtained  with  different  materials  in  different  conditions,  a  few 
of  the  results  of  prominent  investigators  are  give  here.  Thus, 
Strohmer,  with  sugar  beets,  obtained  as  an  average  of  7  fields, 
100  pounds  of  sugar  when  sodium  nitrate  was  used,  to  104 

^  Dr.  A.  Frank,  private  communication. 


86         CYANAMID — MANUFACTURE^    CHI^MISTRY    AND    USi:S 

pounds  of  sugar  when  lime-nitrogen  was  used.^  J.  Kloppep 
obtained  yields  of  sugar  beets  with  no  fertilizer,  sodium  nitrate 
and  lime-nitrogen  respectively  of  loo,  127,  and  149,  while  the 
yields  of  sugar  were  icx),  99,  and  130.  As  an  average  of  10 
cereal  and  root  crops  in  29  field  experiments,  Steglich^  assigned 
the  following  values  to  the  various  materials :  no  fertilizer,  81 ; 
sodium  nitrate,  100;  ammonium  sulphate,  95;  and  lime-nitro- 
gen, 96.  Schneidewind,*  as  an  average  of  5  cereal  and  root 
crops  reports  that  the  increase  in  yield  over  the  fields  un- 
fertilized with  nitrogen  were  comparatively,  sodium  nitrate, 
100;  ammonium  sulphate,  88;  and  lime-nitrogen,  73.  Wagner, 
Director  of  the  Experiment  Station  at  Darmstadt,^  as  a  sum- 
mary of  II  field  tests  on  cereals  with  27  pounds  or  less  of 
nitrogen  per  acre,  reports  the  increased  yield  over  the  fields 
without  nitrogenous  fertilizer,  comparatively  as  follows: 
Sodium  nitrate,  100;  ammonium  sulphate,  87;  and  lime-nitro- 
gen, 94.  Miintz  and  Nottin,  as  an  average  of  11  field  tests 
with  wheat  report  the  following  comparative  yields  obtained: 
Cyanamid,  100 ;  ammonium  sulphate,  94 ;  dried  blood,  96.^ 

USE  AS  A  WEED  DESTROYER. 

In  Germany,  lime-nitrogen  is  used  to  a  considerable  extent 
for  the  destruction  of  obnoxious  weeds,  such  as  wild  mustard, 
occurring  in  grain  crops,  particularly  oats.  The  fine,  dry,  lime- 
nitrogen  is  scattered  either  by  hand  or  by  machine  early  in  the 
morning  when  the  leaves  are  wet  with  dew,  or  after  a  rain,  at 
the  rate  of  60  to  90  pounds  per  acre.  The  lime-nitrogen  readily 
clings  to  the  rough,  hairy,  almost  horizontal  leaves  of  the  wild 
mustard,  and  forms  a  concentrated  solution  in  the  moisture  on 
the  leaves.     This  tends  to  dilute  itself  by  osmosis  and  brings 

^  Oesterr-Ungar. ,  Zeit.  fur  Zuckerindustrie  und  Landwirtschaft, 
XXXV,  No.  VI,  1906,  676. 

2  Fuhling's  Landw.  Zeit.,  56,  No.  15,  1907,  p.  539. 

'  Fuhling's  Landw.  Zeit.,  56,  No.  22,  1907,  p.  780. 

*  Arbeit.  Deut.  Landw.  Ges.,  No.  146,  1908,  p,  116. 

5  Arbeit.  Deut.  Landw.  Ges.,  No.  129,  1907. 

^  Annales  de  I'Institut  National  Agronomique,  2nd  Series,  Vol.  VI, 
No.  I.     See  also  pp.  45-47- 


CYAN  AM  ID — manufacture:,    CHEMISTRY    AND    USES         87 

about  the  destruction  of  the  mustard  within  a  few  days.  The 
application  is  made  when  the  mustard  plant  is  young,  best 
when  it  has  only  four  or  six  leaves.  The  more  leaves  it  has 
the  more  lime-nitrogen  will  be  required.  The  grain  crop  may 
be  affected  a  little  immediately  after  the  application,  and  may 
turn  somewhat  brown  at  the  tips  of  the  leaves,  but  it  will 
quickly  recover  and  become  much  greener  than  the  grain  in 
untreated  fields.  The  leaves  of  the  grain  crops,  especially  oats, 
stand  almost  vertical  and  are  comparatively  smooth  and  waxy, 
so  that  very  little  lime-nitrogen  clings  to  them  and  no 
permanent  damage  is  done.  Practically,  this  method  of  de- 
stroying wild  mustard  is  quite  economical,  since  the  nitrogen 
applied  in  this  way  seems  to  have  as  full  fertilizing  effect  as 
if  it  were  applied  under  the  crop.  The  mustard,  on  the  other 
hand,  is  practically  eradicated. 

DIRECTIONS  FOR  APPLICATION  AS  FERTILIZER. 

Very  little  of  the  Cyanamid  made  in  this  country  is  applied 
alone,  practically  all  of  it  being  used  as  a  part  of  mixed 
fertilizers.  For  the  guidance  of  those  who  wish  to  use  it  with- 
out admixture  with  other  materials,  the  following  suggestions 
are  offered,  although  it  should  be  recognized  that  a  true  test 
of  the  efficiency  of  the  Cyanamid  used  in  this  country  is  made 
only  under  the  conditions  in  which  it  is  usually  applied,  that 
is,  as  a  part  of  a  mixture  containing  phosphoric  acid,  potash, 
and  frequently  other  forms  of  nitrogen. 

Cyanamid  is  least  efficient  when  applied  as  a  top-dressing. 
This  is  probably  due  to  the  quick  reaction  and  fixation  in  the 
soil,  so  that  much  of  the  nitrogen  is  retained  in  the  upper 
layers  of  soil  where  the  plant  roots  do  not  reach  it  readily. 
The  application  should  be  made  in  such  a  way  that  the 
Cyanamid  will  be  buried  about  where  the  plant  roots  are 
expected  to  grow.  It»should  be  scattered  through  the  lower 
layers  of  cultivated  soil  as  much  as  possible,  so  as  to  favor  the 
greatest  spreading  of  the  roots.  In  the  event  of  a  dry  season, 
the  larger  the  root  system,  the  better  will  be  the  ability  of  the 
7 


88         CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

plant  to  withstand  drouth.  Dropping  the  fertilizer  in  narrow 
rows  favors  the  development  of  bunched  root  systems,  which 
will  do  very  well  as  long  as  the  supply  of  fertilizer  lasts  and 
the  water  supply  is  good,  but  are  insufficient  for  the  demands 
of  the  plant  in  dry  weather.  If  the  application  is  large  broad- 
casting one-half  or  two-thirds  of  the  fertilizer  before  plowing, 
or  after  plowing  and  before  harrowing,  with  the  application  of 
the  remainder  in  the  row  before  seeding,  or  along  the  row 
after  the  plants  are  up,  will  be  found  to  produce  the  best 
results.  Care  should  be  taken  that  the  fertilizer  is  well  mixed 
with  the  soil  and  that  pure  fertilizer  and  seed  are  not  in  direct 
contact,  thereby  avoiding  the  so-called  "burning"  of  young 
plants.  When  the  fertilizer  is  applied  alongside  the  rows  after 
the  plants  are  up,  it  should  be  well  worked  in  with  the  cultiva- 
tor or  with  hoes.  Care  should  be  taken  not  to  get  highly  con- 
centrated fertilizers  on  the  leaves  of  the  plant,  especially  if  the 
plant  is  wet.  Since  Cyanamid  is  a  medium-slow-acting  fer- 
tilizer, it  should  be  applied  to  the  crop  not  less  than  70  to  80 
days  before  the  harvest,  in  order  that  the  nitrogen  may  be 
completely  utilized  by  that  crop. 

The  quantity  of  Cyanamid  that  can  be  economically  applied 
at  one  time  is  preferably  limited  to  150  pounds  per  acre. 
Experience  has  shown  that  the  most  economical  utilization 
of  a  nitrogenous  fertilizer  is  obtained  when  it  is  used  in  con- 
junction with  the  other  fertilizing  elements,  phosphorus  and 
potassium.  For  this  reason,  it  is  recommended  that  Cyanamid 
be  used  as  a  part  of  a  fertilizer  mixture,  rather  than  that  it 
be  applied  alone. 

if  Cyanamid  is  to  be  applied  to  very  acid  soils,  such  soils 
should  be  put  in  productive  condition  by  thorough  judicious 
liming  some  time  before  the  application  of  the  fertilizer.  The 
application  of  barnyard  manure  will  help  to  establish  the 
bacteria  that  are  deficient  in  such  soils. 

When  Cyanamid  is  applied  alone,  better  results  will  be  ob- 
tained if  it  is  applied  several  days  before  the  seed  is  sown, 
especially  if  the  applications  are  large.     For  small  applications. 


CYAN  AM  ID — MANUFACTURE,    CHEMISTRY   AND   USES         89 

when  care  is  taken  to  mix  the  fertilizer  well  with  the  soil,  the 
seed  may  be  planted  directly  after  the  fertilizer  is  spread. 
Even  distribution  of  the  Cyanamid  is  facilitated  by  previously 
mixing  it  with  two  to  three  times  its  weight  of  damp  earth. 

USE  OF  COMPLETE  FERTinZER  MIXTURES. 

Since  most  of  the  Cyanamid  used  in  this  country  comes  to 
the  farmer  as  an  ingredient  of  mixed  fertilizers,  it  is  as  a  rule 
not  necessary  to  have  special  instructions  for  its  use.  From 
the  known  chemistry  of  calcium  cyanamide  it  is  very  probable 
that  when  Cyanamid  is  mixed  with  acid  phosphate,  the  phos- 
phoric acid  causes  a  considerable  conversion  of  Cyanamid 
nitrogen  to  the  form  of  urea,  (page  12).  At  any  rate,  the  ordi- 
nary practice  in  the  use  of  mixed  fertilizers  is  such  that  the 
presence  of  Cyanamid  nitrogen  will  not  require  any  modifica- 
tion of  the  usual  practice. 


CHAPTER  X. 


Making  Fertilizer  Mixtures  with  Cyanamid. 


MIXTURES  WITH  AMMONIUM  SALTS. 

Cyanamid  contains  about  55  per  cent.  CaO,  of  which  about 
30  per  cent,  is  present  as  CaCNg,  21  per  cent,  as  Ca(OH)2, 
and  4  per  cent,  as  CaCOg  and  other  forms.  Most  of  the 
calcium,  therefore,  dissociates  readily  and  can  react  when 
brought  into  contact  with  certain  bodies.  In  the  presence  of 
ammonium  sulphate  for  instance,  a  double  decomposition  takes 
place  as  follows: 

Ca(OH),  +  (NH,),SO,  —  CaSO,  +  2NH3  +  2H,0. 

Hence,  if  Cyanamid  and  ammonium  sulphate  are  mixed 
alone  there  will  be  a  large  loss  of  ammonia.  The  same  kind 
of  reaction  takes  place  with  other  ammonium  salts. 

If,  however,  as  is  practically  always  the  case,  there  is 
present  an  adequate  amount  of  acid  phosphate  or  other  acid 
material,  the  acid  of  the  acid  phosphate  immediately  fixes  the 
free  ammonia  and  prevents  its  escape.  The  ammonia  is  com- 
bined probably  as  ammonium  phosphate  or  as  calcium  ammo- 
nium phosphates,  or  both.  To  prevent  loss  of  ammonia,  there- 
fore, it  is  only  necessary  to  have  a  sufficient  amount  of  acid 
material  present  so  that  the  resulting  mixture  will  be  acid  in 
reaction.  This  condition  is  obtained  when  the  amount  of 
Cyanamid  does  not  exceed  100  pounds  of  powdered  Cyanamid 
or  200  pounds  of  granulated  Cyanamid  per  800  pounds  of 
ordinary  acid  phosphate  containing  14  or  16  per  cent,  of 
available  phosphoric  acid.  Such  mixtures  have  been  tested 
in  practical  fertilizer  manufacturing  and  show  no  losses  of 
ammonia.  The  quantity  of  ammonium  sulphate  present  is 
practically  immaterial.  Acid  fish  contains  some  nitrogen  as 
ammonium  sulphate,  and  should  be  mixed  in  accordance  with 
the  above  rule. 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND   USES         QI 

MIXTURES  WITH  ACID  PHOSPHATE. 

In  ordinary  acid  phosphate  analyzing  i6  per  cent,  available 
phosphoric  acid,  there  is  usually  found  about  5  per  cent,  as 
free  phosphoric  acid,  9  per  cent,  as  mono-calcium  phosphate, 
and  2  per  cent,  as  di-calcium  phosphate.  When  such  a  phos- 
phate is  mixed  with  Cyanamid  there  is  obviously  a  neutraliza- 
tion of  free  acid,  and  of  acid  hydrogen  of  the  mono-  and  di- 
calcium  phosphate,  the  extent  of  the  reaction  depending  upon 
the  amount  of  active  lime  introduced  by  the  Cyanamid.  The 
neutralization  is,  of  course,  attended  by  evolution  of  heat, 
and  this  heat  is  the  cause  of  the  unfavorable  results  of  mixing 
large  quantities  of  Cyanamid  with  acid  phosphate. 

In  America,  phosphates  are  sold  on  the  basis  of  their  con- 
tent of  phosphoric  acid  soluble  in  ammonium  citrate  solution 
of  standard  strength,  since  it  has  been  shown  that  there  is  no 
appreciable  difference  in  the  agricultural  value  of  the  water- 
soluble  and  the  citrate  soluble  part  of  the  phosphate.  It  is  to 
the  interest  of  mixers  of  commercial  fertilizers  to  prevent  the 
neutralization  of  the  acid  phosphate  beyond  the  di-calcium 
or  citrate  soluble  stage.  With  increasing  quantities  of  CaO 
the  following  reactions  should  take  place  successively,  but 
with  relatively  decreased  velocity: 

(a)  HgP^Og         -f  CaO  —  CaH,P,0,  +  H,0, 
Phos.  Acid.  Water  Sol. 

(b)  CaH.PA    -h  CaO  --  Ca.H^P.O^  +  H,0, 
Water  Sol.  Citrate  Sol. 

(c)  Ca,H,P,03  +  CaO  —  Ca3P,03  +  H,0. 

The  last  reaction  would  require  a  vast  excess  of  CaO,  since 
CaaHaPaOg  is  practically  insoluble  in  water,  and  is  practically 
undissociated.  This  reaction  does  not  apply  in  the  practical 
mixing  of  Cyanamid  and  acid  phosphate.  There  is,  however, 
a  further  reaction,  tha^  may  take  place  with  prejudicial  results. 

(d)  2Ca,H,P,03  +  Heat  —  Ca^Vfi,  +  CaH^P^^, 
Citrate  Sol.  Cit.  Insol.  Water  Sol. 

It  has  been  found  that  with  a  constant  quantity  of  lime. 


92         CYANAMID — MANUFACTURE:^    CHEMISTRY   AND    USES 

above  a  certain  minimum,  the  proportion  of  citrate  insoluble 
phosphate  formed  is  approximately  a  logarithmic  function  of 
the  temperature.  The  quantity  of  Cyanamid  that  can  be  safely 
mixed  with  acid  phosphate  varies  greatly  with  the  nature  of  the 
acid  phosphate,  particularly  its  content  of  free  acid  and  of 
iron  and  alumina.  For  some  grades  of  acid  phosphate  it  may 
be  as  much  as  120  pounds  of  powdered  Cyanamid,  for  the 
poor  grades  of  acid  phosphate  as  low  as  70  pounds  of  pow- 
dered Cyanamid  to  1,000  pounds  acid  phosphate  in  a  ton 
of  complete  mixture. 

By  the  process  of  granulation,  in  which  the  powdered 
Cyanamid  is  formed  into  particles  which  pass  through  15-mesh 
and  over  50-mesh  standard  screens,  the  chemical  activity  of 
the  Cyanamid  with  acid  phosphate  is  greatly  decreased.  This 
is  mainly  due  to  the  fact  that  the  specific  surface  exposed  by 
particles  of  different  sizes  varies  inversely  as  their  diameters. 
The  number  of  particles  per  unit  of  weight  varies  inversely 
as  the  cubes  of  the  diameters.  One  thousand  particles  one- 
hundredth  of  an  inch  in  diameter,  for  instance,  would  be 
required  to  make  one  granule  one-tenth  of  an  inch  in  diameter, 
and  the  total  surface  exposed  would  be  one-tenth  as  much  as 
before  granulation.  Since  chemical  action  can  take  place  only 
on  the  exposed  surface  of  the  solid  Cyanamid  (the  acid  phos- 
phate having  very  little  fluidity)  it  is  evident  that  the  localiza- 
tion in  a  few  places  of  a  comparatively  large  number  of  widely 
scattered  small  particles  will  greatly  decrease  the  amount  of 
action  that  can  take  place. 

Practically,  it  has  been  found  that  the  chemical  activity  of 
the  granulated  Cyanamid  now  being  manufactured  is 
about  one-half  the  activity  of  the  powdered  Cyanamid; 
hence,  about  twice  as  much  granulated  Cyanamid  can 
be  used  in  acid  phosphate  mixtures  to  produce  the  same  effect 
as  a  given  quantity  of  powdered  Cyanamid.  With  improve- 
ments in  the  process  of  granulation  the  safe  amount  will  be 
probably  further  increased. 


CYANAMID — manufacture:,    CHEMISTRY   AND    USES         93 

OTHER  MIXTURES. 

With  other  materials  commonly  used  in  fertilizer  mixtures 
Cyanamid  can  be  mixed  in  any  quantities,  without  prejudicial 
effect  on  the  valuable  constituents. 

ADVANTAGES  OF  CYANAMID  IN  FERTILIZER 
MIXTURES. 

Drying  Action. — The  free  acids  in  acid  phosphate  are  fre- 
quently the  cause  of  dampness  and  poor  mechanical  condition 
in  mixed  fertilizers,  causing  caking  in  the  bags  and  making 
the  fertilizer  difficult  of  application  through  drills.  To  cor- 
rect this  undesirable  condition  it  is  customary  to  add  to  the 
mixture  various  drying  and  neutralizing  agents.  Since  the 
particles  of  Cyanamid  are  soft  and  porous  and  usually  con- 
tain less  than  i  per  cent,  moisture  they  readily  absorb  free 
moisture  from  the  acid  phosphate  or  other  damp  materials 
with  which  they  come  in  contact.  More  important  is  the 
action  of  the  lime  on  the  free  acids,  calcium  phosphates  tak- 
ing the  place  of  the  sticky  phosphoric  acid,  while  the  heat 
generated  by  the  neutralization  aids  in  dissipating  the  mois- 
ture uniformly  throughout  the  mixture.  This  drying  action 
is  very  valuable  to  the  fertilizer  compounder. 

Preventing  Loss  of  Nitric  Nitrogen. — It  has  long  been  known 
by  fertilizer  manufacturers,  and  has  been  demonstrated  in 
the  laboratory,^  that  when  sodium  or  calcium  nitrate  is  mixed 
with  acid  phosphate,  without  the  further  addition  of  neu- 
tralizing agents,  there  is  a  loss  of  nitrogen  amounting  to  from 
6  to  10  per  cent,  of  the  total  nitrate  nitrogen  added.  The 
loss  is  due  to  the  action  of  the  free  acids  in  the  acid  phosphate 
upon  the  nitrate  salts.  Thus,  with  sodium  nitrate  the  reaction 
probably  is : 

2NaN03  +  H3PO,  — >  Na^HPO,  -f  2HNO3. 

The  nitric  acid  either.volatilizes  as  such  or  is  decomposed  to 

nitrogen  peroxide  and  oxygen  and  escapes  from  the  mixture. 

This  loss  is  prevented  by  Cyanamid  in  two  ways;  the  free 

^  C.  S.  Cathcart,  Jour.  Ind.  and  Eng.  Chem.,  Vol.  3,  No.  i,  191 1. 


94         CYANAMID — MANUFACTURE^    CHEMISTRY   AND    USES 

phosphoric  acid  is  neutralized  by  the  lime  of  the  Cyanamid, 
and  again,  the  free  nitric  acid  or  nitrogen  peroxide  is  neu- 
tralized by  the  Cyanamid  lime  immediately  after  its  forma- 
tion. Whatever  the  mechanism,  it  has  been  shown  by  careful 
experiments  that  Cyanamid  prevents  this  otherwise  serious 
loss  of  nitrate  nitrogen. 

Preventing  Bag-rotting. — A  similar  loss  of  hydrochloric  acid 
gas  occurs  when  potassium  chloride,  or  commercial  muriate 
of  potash,  is  mixed  with  acid  phosphate: 

2KCI  +  H3PO,  —  K,HPO,  +  2HCI. 
This  loss  does  not  decrease  the  commercial  value  of  the 
mixture,  but  the  passage  of  the  acid  gases  through  the  cloth 
of  which  the  bag  is  made  decomposes  the  bag  fiber  and  causes 
so-called  "bag-rotting."  This  destructive  action  is  prevented 
by  the  addition  of  Cyanamid  to  the  mixture,  causing  the  neu- 
tralization of  the  hydrochloric  acid  gas,  or  the  phosphoric 
acid  producing  it. 

To  the  fertilizer  manufacturer,  the  drying  and  neutralizing 
properties  of  Cyanamid  are  decided  advantages,  since  these 
are  not  possessed  by  any  other  high-grade  mineral  fertilizer, 
and  no  extra  charge  is  made  for  them  in  the  selling  price  of 
Cyanamid.  Since  the  cost  of  drying  and  neutralizing  agents 
and  the  extra  mixing  expense  is  saved  if  the  nitrogenous 
ingredient  possesses  these  properties,  Cyanamid  has  been 
received  with  much  favor  by  fertilizer  manufacturers.  Prac- 
tically the  entire  output  of  the  American  Cyanamid  Company 
is  sold  in  this  way. 


CHAPTER  XI. 


Permanganate  Availability  of  Cyanamid. 


In  order  to  have  a  ready  means  of  determining  the  agricul- 
tural availability  of  the  nitrogen  in  various  organic  compounds, 
certain  chemical  methods  have  been  adopted  that  approxi- 
mately measure  this  property.  The  permanganate  availability 
methods  are  in  general  use  for  this  purpose.  It  is  generally 
assumed  that  nitrogen  compounds  soluble  in  water  are  readily 
utilized  as  plant  food,  but  it  is  also  recognized  that  nitrogen 
compounds  insoluble  in  water  may  be  utilized  by  the  plant  in 
the  course  of  growth.  It  seems  to  be  generally  true  of  organic 
nitrogenous  compounds  that  the  solubility  in  water,  together 
with  the  relative  ease  with  which  the  insoluble  parts  are  de- 
composed by  potassium  permanganate  bears  a  regular  relation 
to  the  agricultural  availability  of  the  fertilizer.  It  is  interest- 
ing to  examine  whether  Cyanamid  takes  its  proper  place  in  the 
permanganate  availability  series  of  values  as  compared  with  its 
agricultural  availability,  and  which  of  the  permanganate 
methods  gives  the  truest  results. 

The  following  experiments  on  the  solubility  of  Cyanamid 
nitrogen  in  water,  and  its  behavior  under  the  influence  of 
potassium  permanganate,  were  made  under  the  direction  of  the 
author  in  October,  19 12.  The  Cyanamid  used  was  a  low 
grade,  granulated  material  analysing  as  follows: 

Nitrogen 13-58  per  cent. 

I.ime(CaO)  50.57 

Moisture i  .83        '  * 

Carbon  dioxide 4.00        " 

Size  of  granules 15  to  50  mesh 

EXPERIMENT  I. 

Solubility  on  Filtej . — Samples  of  i  gram,  2  grams,  4  grams 
and  8  grams  of  granulated  Cyanamid  were  placed  on  filter 
papers  and  washed  with  successive  portions  of  distilled  water 
at  25°  C.  until  the  volume  of  filtrate  reached  250  cc.     The 


96         CYANAMID — MANUFACTURE),    CHEMISTRY   AND   USES 

nitrogen  content  of  each  filtrate  was  determined  with  the  fol- 
lowing results : 

Sample  Grams  of  Grams  of  Per  cent,  of 

grams  N.  in  sample  N.  in  filtrate      total  N.  in  filtrate 

1 0.1358  0.1227  90-4 

2 0.2716  0.2357  86.8 

4 0.5432  0.4729  87.1 

8 1.0864  0.8103  74.6 

EXPERIMENT  n. 
Solubility  in  Flasks. — Samples  of  2,  4,  8,  17  and  32  grams 
of  granulated  Cyanamid  were  placed  in  Erlenmeyer  flasks  and 
each  covered  with  400  cc.  of  distilled  water  at  25°  C.  The 
flasks  were  stoppered,  and  allowed  to  stand  24  hours,  with 
occasional  shaking.  They  were  filtered  through  dry  filters 
without  washing  and  nitrogen  was  determined  in  each  filtrate, 
with  the  following  results : 

Sample  Grams  of  Grams  of  Per  cent,  of 

grams  N.  in  sample  N.  in  filtrate      total  N.  in  fillrate 

2 0.2716  0,2548  93.9 

4 0.5432  0.5102  93.9 

8 1.0864  1.0119  93.1 

16 2.1728  2.0087  92.5 

32 4.3456  3-9588  91. 1 

EXPERIMENT  HI. 
Rate  of  Solution  in  Flasks. — In  each  of  five  flasks  was  placed 
2  grams  of  granulated  Cyanamid  and  250  cc.  distilled  water  at 
25°  C.  Each  flask  was  shaken  for  10  minutes  continuously, 
after  addition  of  the  sample,  and  then  only  occasionally.  After 
filtration  without  washing,  nitrogen  was  determined  in  the 
filtrate.     The  following  results  were  obtained: 

Gram  of  Gram  of  Per  cent,  of 

Time                            N.  in  sample  N.  in  filtrate       total  N.  dissolved 

10  minutes 0.2716  0.2055  75-6 

30        **        0.2716  0.2298  84.6 

2  hours 0.2716  0.2403  88.5 

6      *'       0.2716  0.2433  89.6 

24      "       0.2716  0.2480  91.3 

Neutral  Permanganate  Method. — One  of  the  permanganate 
availability    methods    formerly    much    used    is    the    neutral 


CYANAMID — MANU]?ACTURE:,    CHE^MISTRY    AND    USEJS         97 

permanganate  method  described  in  Bureau  of  Chemistry,  U. 
S.  Department  of  Agriculture,  Bulletin  107,  page  10.  In  this 
method  a  sample  of  fertilizer  containing  about  0.075  grams  of 
nitrogen  is  digested  for  30  minutes  on  a  water  or  steam  bath 
with  125  cc.  of  potassium  permanganate  solution  containing  2 
grams  of  potassium  permanganate.  It  is  then  diluted  with 
100  cc.  cold  water  and  filtered  and  washed  until  the  total  filtrate 
amounts  to  400  cc.  The  nitrogen  is  determined  in  the  residue ; 
the  percentage  of  nitrogen  removed  is  called  the  availability. 
To  obtain  the  effect  of  the  potassium  permanganate  this 
method  was  used,  first,  with  125  cc.  of  distilled  water  in  place 
of  the  permanganate,  and  second,  with  the  125  cc.  of  perman- 
ganate solution. 

Per  cent. 

Availability  with  water  in  place  of  permanganate 94.34 

Availability  with  permanganate 87.54 

Since  the  only  difference  in  the  above  experiments  was  the 
absence  of  the  2  grams  of  potassium  permanganate  in  the  first 
run,  it  is  evident  that  potassium  permanganate  has  the  effect 
of  converting  about  7  per  cent,  of  the  total  nitrogen  into  in- 
soluble compounds. 

Alkaline  Permanganate  Method. — In  this  method  the  avail- 
ability is  measured  by  the  amount  of  ammonia  that  is  formed 
and  distilled  from  an  alkaline  permanganate  solution.  An 
amount  of  sample  containing  0.045  grams  of  nitrogen  is 
digested  below  the  boiling  point  with  100  cc.  of  solution  con- 
taining 15  grams  of  sodium  hydroxide  and  1.6  grams  of 
potassium  permanganate,  for  thirty  minutes.  It  is  then  boiled 
and  the  distillate  collected  until  85  cc.  is  obtained.  The  per- 
centage of  nitrogen  distilled  over  as  ammonia  represents  the 
availability.  In  order  to  learn  the  effect  of  each  reagent  a  run 
was  made  by  this  method  using,  first,  100  cc.  of  distilled  water 
in  place  of  the  alkaline  permanganate  solution;  second,  a  run 
was  made  with  15  grams  of  sodium  hydroxide  in  100  cc.  of 
solution,  and  a  third  run  was  made  with  both  sodium  hydroxide 
and  potassium  permanganate  in  100  cc.  solution.  The  results 
were  as  follows : 


98         CYANAMID — manufacture:,    CHEMISTRY   AND    USES 

Per  cent. 

Availability  with  water  alone 13.79 

Availability  with  water  and  sodium  hydroxide 53.90 

Availability  with  water  and   sodium  hydroxide  and 

potassium  permanganate 4.75 

This  experiment  shows  that  the  nitrogen  in  Cyanamid  is  only 
slowly  converted  into  ammonia  by  the  action  of  boiling  water 
alone,  and  that  it  is  much  more  rapidly  converted  into  ammonia 
in  the  presence  of  sodium  hydroxide.  By  the  action 
of  potassium  permanganate,  however,  the  formation  of 
ammonia  is  almost  completely  prevented,  even  in  the  presence 
of  sodium  hydroxide. 

Hence,  in  the  above  methods  the  addition  of  potassium  per- 
manganate has  the  opposite  effect  from  what  was  intended  to 
be  the  function  of  potassium  permanganate,  namely  to  make 
insoluble  compounds  soluble  and  to  convert  complex  com- 
pounds to  the  ammonia  form.  In  the  case  of  Cyanamid,  the 
neutral  permanganate  method  makes  some  water-soluble  com- 
pounds insoluble,  and  the  alkaline  permanganate  method  practi- 
cally prevents  the  formation  of  any  ammonia. 

The  method  which  is  lately  coming  into  favor  is  the  modified 
alkaline  permanganate  method  adopted  by  the  Agricultural 
Experiment  Stations  of  New  York,  New  Jersey  and  the  New 
England  States  on  March  4,  191 1. 

Modified  Alkaline  Permanganate  Method. — This  differs  from 
the  other  methods  in  that  an  amount  of  sample  equivalent  to 
0.050  grams  of  nitrogen  is  first  washed  on  a  filter  with  distilled 
water  at  room  temperature  until  250  cc.  of  filtrate  is  obtained. 
This  is  intended  to  remove  all  the  water-soluble  nitrogen.  As 
a  matter  of  fact,  it  removes  about  87  per  cent,  out  of  a  possible 
94  per  cent,  of  water  soluble  nitrogen  in  a  low-grade  Cyanamid, 
and  about  89  per  cent,  out  of  a  possible  96  per  cent,  in  a  high- 
grade  Cyanamid.  The  ''insoluble"  residue  is  digested  for  thirty 
minutes  in  a  flask  with  120  cc.  of  solution  containing  2.5  grams 
potassium  permanganate  and  1.5  grams  sodium  hydroxide,  and 
the  ammonia  is  then  distilled  by  boiling  until  95  cc.  of  distillate 
is  obtained.    The  sum  of  the  percentage  of  water  soluble  nitro- 


CYANAMID — manufacture;,    CHEMISTRY   AND    USES         99 

gen  and  of  nitrogen  in  the  distillate  represents  the  availability. 
By  this  method  the  sample  used  in  these  experiments  gave 
90.20  per  cent,  availability. 

C.  S.  Cathcart,  State  Chemist  at  the  New  Jersey  Agricultural 
Experiment  Station,  made  some  experiments  with  samples  of 
powdered  Cyanamid,  using  the  regular  modified  alkaline  per- 
mangate  method,  with  the  following  results. 

Sample  number                              284  285  294  295  308 

Per  cent.  Per  cent.  Per  cent.  Per  cent.    Per  cent. 

Qualitative  test  for  nitrates .     none  none  none  none  none 

Total  nitrogen. 15.76  13.57  13.29  14.00  16.40 

Nitrate  and  ammoniacal 

(Ulsch-Street) 6.98  5.53  3.50  4.72  7.32 

Ammonia  salts  (magnesia). .     0.92  0.57  0.45  0.55  0.91 

Water  soluble  (total) 14.15  11.93  12.23  12.88  14.67 

Water  insoluble 1.25  1.64  1.06  1.12  1.73 

Active  insoluble  (distilled 
from  alkaline  permanga- 
nate)      0.17  0.17  0.25  0.32  0.33 

Inactive  insoluble 1.08  1.47  0.81  0.80  1.40 

Total  nitrogen  as  water  solu- 
ble and  active  insoluble.  93.1  ^9.2  93.4  94.3  91.5 

It  is  interesting  to  note  that  as  much  as  40  per  cent,  of  the 
Cyanamid  nitrogen  is  converted  to  ammonia  by  the  reducing 
action  of  the  iron  and  sulphuric  acid  used  in  the  Ulsch-Street 
method.^  The  amount  of  ammoniacal  nitrogen  originally  pre- 
sent is  shown  by  magnesia  distillation  to  be  from  3  to  6  per 
cent,  of  the  total  nitrogen.  The  qualitative  test  showed  no 
nitrates  present. 

The  water-soluble  nitrogen  with  one  washing  of  250  cc. 
distilled  water  is  from  87  to  92  per  cent,  of  the  total,  the 
average  being  90.6  per  cent.  By  treatment  with  alkaline  per- 
manganate the  available  nitrogen  is  found  to  be  92.5  per  cent, 
as  an  average  of  the  five  samples. 

In  order  to  determine  the  effect  of  a  more  thorough  initial 
washing,  Cathcart  repeated  the  availability  experiments  wash- 
^  For  Ulsch-Street  Method  see  U.  S.  Dept.  of  Agr.  Bureau  of  Chem., 
Bui.  107.,  or  Wiley's  Principles  and  Practice  of  Agricultural  Analy- 
sis, Vol.  I,  p.  445. 


lOO      CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES 

ing  each  sample  three  times  with  250  cc.  water  each  time.  The 
following  results  were  obtained : 

Sample  number  284  285  294  295  308 

Per  cent.     Per  cent.    Per  cent.     Per  cent.     Per  cent. 

Total  nitrogen 15.76  13.57  13-29  14.00  16.40 

Soluble  nitrogen,  1st  250  cc.  14.71  12.13  11.89  12.78  14.50 
*'          "          2nd     **  .  0.08  0.32  0.32  0.32  0.49 
"          "         3rd      '*   .  0.12  0.12  0.12  0.08  0.33 
Total  soluble  nitrogen  ... .  14.91  12.57  12.32  13.18  15.32 
Active  insoluble  nitrogen.  0.14  0,22  0.23  0.22  0.31 
Inactive       "              '«     ...  0.71  0.78  0.73  0.60  0.77 
Total  nitrogen  as  water  sol- 
uble and  active  insoluble  95.5  94.3  94.5  95.7  95.3 

It  is  seen  that  with  this  change  in  the  procedure  the  water- 
soluble  nitrogen  averages  93.5  per  cent,  and  the  total  available 
95.1  per  cent. 

The  percentage  of  available  nitrogen  revealed  by  the 
modified  alkaline  permanganate  method  is  practically  a  ques- 
tion of  the  solubility  and  the  rate  of  solution  of  Cyanamid 
nitrogen  in  the  initial  washing  with  distilled  water.  The  in- 
fluence of  size  of  sample  and  of  rate  of  solution  is  shown  in 
the  preliminary  experiments  on  page  96.  It  is  evident  that  to 
determine  the  true  amount  of  water-soluble  nitrogen  in 
Cyanamid  by  the  modified  alkaline  permanganate  method  a 
longer  period  of  contact  should  be  allowed  between  sample 
and  solvent  in  the  initial  washing,  or  more  solvent  should  be 
used.  The  simplest  way  would  be  to  let  the  sample  stand  in  a 
flask  with  distilled  water  for  24  hours  and  filter,  or  to  agitate 
on  a  shaking  machine  for  about  three  hours. 

Whether  or  not  the  availability  determined  by  the  perman- 
ganate methods  corresponds  with  the  fertilizer  efficiency  of 
Cyanamid  is  a  question  principally  of  determining  what  the 
fertilizing  efficiency  is,  since  the  permanganate  methods  are 
easily  carried  out  in  the  laboratory.  The  concensus  of  opinion 
seems  to  be  that  Cyanamid  has  about  the  fertilizing  value  of 
sulphate  of  ammonia,  and  this  is  about  95  per  cent,  of  the 
efficiency  of  nitrate  of  soda,  as  an  average  of  all  kinds  of 
conditions,    favorable  and  unfavorable,  that  might  occur  in 


CYANAMID — manufacture;,    CHEMISTRY   AND   USES      lOI 

agricultural  practice.  Both  sulphate  of  ammonia  and  nitrate 
of  soda,  however,  show  an  availability  of  lOO  per  cent,  by  the 
permanganate  methods,  while  Cyanamid  shows  about  87  to  89 
per  cent,  by  the  neutral  permanganate  method,  4  to  8  per  cent, 
by  the  alkaline  permanganate  method,  90  to  94  per  cent,  by  the 
modified  alkaline  permangante  method,  and  94  to  96  per  cent. 
by  simple  solution  in  water  for  24  hours.  The  neutral  and  the 
modified  alkaline  methods  therefore  approximate  to  a  certain 
extent  the  values  that  they  should  represent,  the  straight 
alkaline  method  is  wholly  unsuitable,  while  the  simple  solution 
in  water  gives  the  most  significant  results. 


CHAPTER  XII. 


Fire  and  Water  Hazard  of  Cyanamid. 


The  combustibility  of  Cyanamid  and  its  susceptibility  to 
damage  by  fire  and  water  have  been  thoroughly  investigated 
by  the  Underwriters'  Laboratories  of  Chicago,  111.  The  fol- 
lowing results  were  obtained  through  the  courtesy  of  Mr. 
A.  H.  Nuckolls,  Chemical  Engineer,  of  the  Underwriters' 
Laboratories,  and  are  a  part  of  the  report  prepared  for  the 
information  of  fire  insurance  companies : 

"The  object  of  the  investigation  was  to  determine  the  nature 
of  recommendations  to  be  made  relative  to  issuance  of  an 
opinion  upon  the  fire  hazard  of  the  product.  This  report 
does  not  deal  with  the  hazards  of  mixtures  of  this  product 
with  other  fertilizers." 

"Test  for  Flammable  Gases. — Tests  for  flammable  gases  were 
conducted  by  placing  about  5  pounds  of  the  product  in  a 
large  bottle,  about  6  inches  internal  diameter  by  16  inches  in 
height,  and  adding  an  excess  of  water.  The  bottle  was  pro- 
vided with  a  loose  fitting  stopper  to  which  wires  were  attached 
for  producing  an  electric  spark  inside  of  the  bottle.  The 
spark  was  produced  at  intervals  of  about  15  minutes  at  the 
beginning  of  the  test.  The  bottle  was  allowed  to  stand  for 
10  days,  the  spark  being  produced  about  every  3  to  4  hours 
except  during  the  night.  The  test  was  repeated  employing 
a  gas  testing  flame  instead  of  the  electric  spark  and  also 
varying  the  proportions  of  gas  and  air. 

"No  analysis  of  the  gas  evolved  was  conducted.  .  .  . 
Mixtures  of  air  with  gases  evolved  when  test  samples  were 
treated  with  water  did  not  ignite  or  burn  when  brought  into 
contact  with  electric  spark  and  gas  flame." 

"Spontaneous  Heating  Tests. — Acceleration  Test. — This  test 
was  conducted  by  means  of  an  apparatus  consisting  essentially 
of  a  wire  gauze  cylinder  about  15^  inches  in  diameter  and 
6    inches   long,    which    is    surrounded   by    a   double- jacketed 


CYANAMID — MANUFACTURE,    CHEMISTRY    AND    USES       IO3 

copper  water-bath  provided  with  a  tight  fitting  top  or  lid, 
a  thermometer  and  inlet  and  outlet  tubes  to  admit  air.  The 
sample  was  placed  in  the  wire  gauze  cylinder,  and  the  ther- 
mometer inserted  so  that  its  bulb  was  within  the  sample  near 
its  center.  The  temperature  of  the  bath  was  maintained  at 
100°  C.  for  4  weeks.  For  the  first  6  hours  of  the  test,  tem- 
perature readings  were  taken  every  half  hour.  Afterwards, 
readings  were  taken  twice  daily  until  the  test  was  concluded. 
"The  thermometer  showed  that  the  internal  temperature  of 
the  sample  remained  at  approximately  ioo°  C.  during  the 
tests." 

''Test  with  Water. — About  lo  pounds  of  the  product  were 
placed  in  a  wooden  cylinder,  approximately  lo  inches  in  height, 
and  lo  inches  internal  diameter,  the  walls  of  the  cylinder 
being  about  i  inch  in  thickness.  The  temperature  of  the 
sample  was  allowed  to  become  the  same  as  that  of  the  room, 
and  then  about  4  pounds  of  water,  the  temperature  of  which 
was  observed,  were  added  with  stirring.  The  mixture  was 
then  allowed  to  stand  and  its  temperature  observed  for  a 
period  of  about  a  week. 

Test  started  at  10.30  A.  M.  Degrees  C. 

Temperature  of  room  during  test,  about 18 

"  "  water  at  start 18 

*•  "  test  sample  of  product  at  start 17 

"  '*  mixture  at  11.00  A.  M.,  about 20 

"No  material  rise  in  the  temperature  of  the  mixture  was 
observed." 

"Acid  Tests. — One  pound  samples  of  the  product  were 
treated  with  concentrated  hydrochloric,  sulphuric,  and  nitric 
acids  and  the  results  observed. 

"The  acids  reacted  readily  with  the  samples  with  consid- 
erable evolution  of  Ifeat,  compounds  of  these  acids  and  lime 
being  produced,  and  the  Cyanamid  (CaCNg)  was  also  attacked 
and  decomposed.  No  combustion  or  explosive  action  took 
place." 
8 


I04      CYANAMID — MANUFACTURER,    CHEMISTRY   AND    USES 

"Behavior  of  Product  when  Heated. — Two  20-gram  test 
samples  were  heated  in  a  large  porcelain  dish  by  means  of  a 
Bunsen  burner.  The  heat  was  gradually  increased  until  the 
temperature  of  the  samples  was  above  a  bright  red  heat. 
During  the  test  a  small  gas-testing  flame  was  constantly 
applied  to  the  samples. 

"At  the  start  oil  vapors  were  given  off  but  not  in  sufficient 
quantity  to  form  a  flame.  The  samples  were  decomposed 
but  no  material  amount  of  combustion  occurred." 

"Test  with  the  Oil  Used. — A  sample  of  oil  employed  in  the 
manufacture  of  Cyanamid  was  obtained  directly  from  the 
manufacturer.  Small  samples  of  the  oil  were  also  obtained 
from  the  product  by  extraction  with  petroleum  ether. 

''Specific  Gravity. — Specific  gravity  was  obtained  roughly 
by  means  of  a  Be.  hydrometer.  The  specific  gravity  was 
found  to  be  approximately  30°  Be.  at  19°  C. 

''Flashing  Point. — The  flashing  point  was  determined  with 
the  Pensky-Martens  tester,  the  standard  method  of  test  with 
this  apparatus  being  followed.  The  flashing  point  was  found 
to  be  150°  C.  (221°  F.)  closed  cup. 

"Evaporation. — An  evaporation  test  was  conducted  by  heat- 
ing about  y2  gram  of  a  sample  of  the  soil,  spread  out  on  a 
watch-glass,  for  5  hours  at  100°  C.  in  an  ordinary  oven  and 
determining  the  loss  of  weight  of  the  sample.  The  loss  by 
evaporation  was  found  to  be  i.i  per  cent,  by  weight  in  4 
hours. 

"Spontaneous  Heating. — This  test  was  conducted  by  heating 
14  grams  of  the  oil,  disseminated  over  7  grams  of  cotton,  at 
a  temperature  of  100°  C.  for  48  hours  in  an  apparatus  con- 
sisting essentially  of  a  wire  gauze  cylinder,  about  i^  inches 
in  diameter  and  6  inches  long,  surrounded  by  a  double- jacketed 
copper  water-bath  provided  with  a  tight  fitting  top,  thermom- 
eter, inlet  and  outlet  tubes  to  admit  air.  The  oiled  cotton  was 
placed  in  the  wire  gauze  cylinder,  and  the  thermometer  in- 


CYANAMID — MANUFACTURE,    CHEMISTRY   AND    USES       IO5 

serted  so  that  its  bulb  was  within  and  near  the  center  of  the 
oiled  cotton.  Observations  were  made  to  note  if  any  differ- 
ence between  the  temperature  of  the  sample  and  the  water- 
bath  occurred. 

"The  internal  temperature  of  the  test  sample  remained 
slightly  below  ioo°  C.  during  the  first  5  hours  of  heating,  and 
never  exceeded  icx)^  C.  the  temperature  of  the  surrounding 
bath." 

"General  Behavior  when  Treated  with  Water. — A  stream  of 
water  at  about  75  pounds  pressure  from  a  ^  inch  nozzle  was 
applied  to  a  bag  for  15  minutes,  the  stream  being  directed  so  as 
to  wet  the  entire  external  surface  of  the  bag.  The  bag  was 
then  allowed  to  stand  about  a  week,  and  an  average  sample  was 
analyzed  according  to  the  method  of  Gunning. 

"The  sample  did  not  readily  absorb  water,  owing  to  the 
presence  of  oil  which  retarded  immediate  contact  of  the  water 
with  the  lime-nitrogen  compound.  Water  was,  however, 
gradually  absorbed  with  a  very  slow  evolution  of  gas  in  small 
quantity.  A  marked  odor  of  ammonia  was  noted.  When 
allowed  to  dry  in  air,  the  sample  hardened  to  some  extent,  or 
in  other  words  'caked.'  This  'caking'  was  in  a  measure  due  to 
absorption  of  carbon  dioxide  from  the  air. 

Per  cent. 

Nitrogen  in  sample  before  wetting 14.44 

Nitrogen  in  sample  after  wetting 13. 10 

Apparent  loss  of  nitrogen 1.34 

The  following  conclusions  were  drawn  with  regard  to  the 
fire  and  water  hazard  of  Cyanamid : 

"It  is  readily  decomposed  by  high  temperatures,  and  also  by 
mineral  acids  which  attack  it  somewhat  violently  with  the 
evolution  of  considerable  heat.  Its  decomposition  by  water  is 
not  accompanied  by  a  material  rise  in  temperature  or  the 
formation  of  hazardous  products  in  dangerous  quantity.  It  is 
not  liable  to  spontaneous  ignition. 

"The  product  is  non-flammable,  and  is  not  combustible  to 


I06      CYANAMID MANUI^ACTURE,    CHISJMISTRY   AND    USES 

a  material  extent.  The  product  is  decomposed  by  high  tem- 
peratures such  as  are  produced  in  burning  buildings.  It  will 
be  noted  that  a  relatively  small  amount  of  oil  (4.2  per  cent.) 
and  carbon  13.25  per  cent.)  are  present.  The  high  tempera- 
ture to  which  the  free  carbon  is  subjected  in  the  electric 
furnace  renders  it  sufficiently  graphitic  to  be  difficulty  com- 
bustible. 

"The  product  is  susceptible  to  damage  to  a  material  extent 
by  fire  or  water.  The  product  does  not  readily  take  up  water, 
and  is  not  a  good  conductor  of  heat.  In  case  of  fire  it  will, 
therefore,  probably  be  only  partially  damaged  by  the  heat  and 
water. 

"The  product  is  considered  non-hazardous  except  in  respect 
to  susceptibility  to  damage  by  fire  and  water." 

In  the  process  of  manufacture,  the  cans  containing  the  crude 
calcium  cyanamide  are  withdrawn  from  the  nitrifying  ovens  at 
a  temperature  of  more  than  1,000°  C,  and  are  allowed  to  cool 
in  the  open  air,  without  noticeable  injury  to  the  calcium 
cyanamide. 


INDEX 


Absorption  of  cyanamide  in  soil, 
39-42,  60. 

Acetic  acid,  action  on  cyana- 
mide, 12. 

Acetylene,  73. 

Acid  fish,  in  Cyanamid  fertilizer 
mixtures,  90. 

Acid  phosphate,  mixtures  with 
Cyanamid,  91-94. 

Acids,  action  on  cyanamide,  12,  13, 
103,  104,  106. 

Acid  soils,  fertilizers  on,  70,  74,  83. 

Activity  of  Cyanamid  with  potas- 
sium permanganate,  95-101. 

Addition  compounds  of  cyana- 
mide, 13. 

Aeration,  influence  on  cyanamide 
conversion,  47. 

Air,  effect  on  cyanamide  decom- 
position, 47. 

Alkaline  permanganate  method, 
97-101. 

Aluminium  hydroxide,  effect  on 
cyanamide  decomposition,  52, 
53,  54. 

American  Cyanamid  Co.,  capacity 
of  factories,  3. 

Amidodicyanic  acid,  15 ;  identi- 
fication of,  23. 

Ammelide,  12. 

Ammeline,  12  ;  identification,  23. 

Ammonia  from  Cyanamid,  8,  12  ; 
loss  in  storage,  24-31. 

Ammonia,  loss  of  in  fertilizer  mix- 
tures, 90. 

Ammonium  compounds,  formation 
in  cyanamide  decomposition,  45, 
46. 

Ammonium  salts  in  Cyanamid  fer- 
tilizer mixtures,  90. 


Ammonium  sulphate,  excessive  ap- 
plications, 69  ;  use  in  Cyanamid 
mixtures,  90. 

Analysis  of  typical  Cyanamid,  8. 

Analysis— see  analytical  methods. 

Analytical  methods :  total  nitro- 
gen, 19,  20 ;  cyanamide,  nitro- 
gen, 20-22  ;  dicyandiamide  nitro- 
gen, 20-22  ;  amidodicyanic  acid, 
23  ;  ammeline,  23. 

Application  of  excessive  quantities 
of  Cyanamid,  69-84 ;  normal 
quantities,   73,  87,  89. 

Ashby,  36. 

Aso,  K,  77,  78. 

Availability  of  Cyanamid — perman- 
ganate methods,  95-101. 

Available  phosphoric  acid,  in 
Cyanamid   mixtures,    91-92. 

Bacteria — effect  on  decomposition 
of  cyanamide,  32-36  ;  not  neces- 
sary in  decomposition  of  cyana- 
mide to  urea,  40,  43,  44,  45,  50, 
56,  58,  59- 

Bags,  storage  of  Cyanamid  in,  25. 

Bag-rotting,  prevention  of,  94. 

Barium  carbide,  2. 

Barium  cyanamide,  2. 

Bases,  action  on  cyanamide,  12,  13. 

Basic  calcium  cyanamide,  16. 

Bauxite,  effect  on  cyanamide  de- 
composition, 52,  53. 

Behrens,  36. 

Bineau,  10. 

Brioux,  Ch.  Decomposition  pro- 
ducts in  exposed  Cyanamid,  29, 
30 ;  modified  Caro  method  for 
analysis  of  cyanamide  and  di- 
cyandiamide, 21 ;  pot  tests,  77. 

Bunsen,  i. 

Calciocianamide,  definition,  4. 

Calcium  acid  cyanamide,  14. 


io8 


INDEX 


Calcium — effect  on  decomposition 
of  cyanamide  in  soil,  33. 

Calcium  carbide,  analysis,  6 ;  effect 
of  in  fertilizer,  73  ;  manufacture 
of,  2,  4. 

Calcium  Cyanamid,  definition  of,  4. 

Calcium  cyanamide,  definition  of, 
4  ;  formation,  2  ;  properties,  14  ; 
temperature  of  formation,  2 ; 
volatility,  6.  See  also  Cyanamid, 

Calcium  cyanamide  carbonate,  16, 
17,  38. 

Calcium  cyanamide,  definition,  4. 
See  also  calcium  cyanamide  and 
Cyanamid. 

Calcium  hydroxide,  effect  on  cyana- 
mide decomposition,  48.  See  al- 
so calcium,  lime. 

Calcium  nitrate,  excessive  appli- 
cations, 69. 

Carbide.  See  calcium  carbide,  ba- 
rium carbide. 

Carbon,  effect  on  cyanamide  de- 
composition, 50. 

Carbon  dioxide,  action  on  calcium 
cyanamide,  16 ;  action  in  soil, 
37,  38 ;  effect  on  Cyanamid  in 
storage,  24-28. 

Cannizzare,  10. 

Caro,  Dr.  Nicodem,  i,  2,  6,  11,  17; 
method  of  analysis,  20. 

Catalytic  agents,  in  cyanamide  de" 
composition,  42,  48-56,  58. 

Cementing  powders,  9. 

Cereal  crops,  86. 

Chloroform— as  sterilizing  agent, 
33,  57- 

Cladosporium,  in  decomposition  of 
cyanamide,  34-36. 

Climate,  effect  on  Cyanamid  in 
storage,  24-31. 

Cloez,  10. 

Colloids — effect  on  cyanamide  de- 
composition, 48-59. 

Commercial  Cyanamid.  See  Cyana- 
mid. 

Commercial  derivatives,  8. 


Complete  fertilizer  mixtures,  89-94. 

Conversion  of  available  phosphoric 
acid  in  Cyanamid  mixtures,  91-92. 

Copper  oxide  process,  5. 

Concentration  of  cyanamide,  effect 
on  decomposition,  40,  42,  46,  47. 

Cyanamid:  Agricultural  use,  83-89; 
analysis,  7,  8  ;  analytical  meth- 
ods, 19-22  ;  availability,  95-101  ; 
decomposition  in  soil,  32-59  ;  de- 
finition of  term,  4 ;  derivatives, 
8-18  ;  development  of  industry, 
1-8  ;  excessive  applications,  69  ; 
fertilizer  mixtures,  90-94 ;  fire 
and  water  hazard,  102-106;  manu- 
facture, 4-7  ;  nitrification,  62-64  ; 
retention  in  soil,  60-61  ;  solu- 
bility, 95-96;  storage,  24-31; 
toxicity,  65-82.  See  also  cyana- 
mide. 

Cyanamide  :  Action  of  acids,  12  ; 
alkalies,  12;  heat,  11;  oxidizing 
and  reducing  agents,  13,  95-101 ; 
analysis  of,  19-21 ;  decomposition 
in  soil,  32-59  ;  definition  of  term, 
4  ;  derivatives,  13-17  ;  discovery, 
10;  properties,  11.  See  also 
Cyanamid. 

Cyanides  :  Absent  in  Cyanamid,  2, 
8  ;  manufacture,  8  ;  part  in  de- 
velopment of  Cyanamid  indus- 
try, I. 

Cyanuric  acid,  12. 

Decomposition  of  Cyanamid  in  soil, 
32-59 ;  effect  of— aeration,  47  ; 
aluminum  hydroxide,  52-54  ; 
bauxite,  52-53  ;  colloids,  48-59  ; 
concentration  of  solution,  40, 
carbon,  50  ;  electrolytes,  48 ; 
glass  sand,  52-54  ;  heat,  43  ;  iron 
oxide,  52-54,  56;  iron  hydrox- 
ide, 54,  55  ;  kaolin,  52-53  ;  silicic 
acid,  54  ;  soil,  32-49  ;  sterile  soil, 
44,  50,  56;  umber,  52  ;  tempera- 
ture, 43  ;  zeolites,  49;  products 
formed,  43-45,  5i  :  stages  in,  37, 
38.  57. 


INDEX 


109 


Decomposition  of  Cyanamid  in  stor- 
age, 28,  29. 

Definitions  of  terms  used  in  Cyan- 
amid industry,  3-4. 

Derivatives  of  Cyanamid,  8-18. 

Di-calcium  phosphate  in  Cyanamid 
mixtures,  91-92. 

Dicyandiamide ;  commercial  pro- 
duction, 9;  conversion  in  soil,  77; 
decomposition,  75,  76;  formation 
in  Cyanamid,  11,  43,44,  5i,  75; 
method  of  treating  subject,  74; 
properties,  17,  18;  pure  versus 
impure,  77-82  ;  toxicity,  77-82. 

Dicyandiamidine,  analysis,  21  ; 
properties,  18. 

Dimetal  salts  of  cyanamide,  13. 

Discovery  of  Cyanamid,  i. 

Drying  action  of  Cyanamid  in  fer- 
tilizer mixtures,  93. 

Duration  of  Cyanamid  nitrogen  in 
soil,  64. 

Dye  industry,  use  of^dicyandiamide 
in,  9. 

Efficiency  of  utilization  of  nitrogen 
in  fertilizers,  69,  84. 

Electric  furnace,  i,  4. 

Electrolytes,  effect  on  cyanamide 
decomposition,  47. 

Equilibrium,  temperature,  6  ;  pres- 
sure, 6. 

Errors  in  fertilizer  experiments,  84, 
85. 

Excessive  applications,  effect  of, 
69,  72,  82,  84. 

Experimenting  with  fertilizers,  69, 
83-86. 

Explosives,   Cyanamid  derivatives 

for  use  in,  9. 
Exposure  of  Cyanamid,*  effect  of, 

25-31. 
Factory  storage  of  Cyanamid,  24. 
Ferrodur,  9. 


Fertilizer  :  excessive  application  of, 
69-73,  84  ;  mixtures  with  Cyana- 
mid, 89-94;  preparation  of  Cyana- 
mid as  material  for,  7  ;  use  of 
Cyanamid  as,  73,  87,  89. 

Fineness  of  Cyanamid,  7. 

Fire  and  water  hazard  of  Cyanamid, 
102-106. 

First  stage  of  decomposition  of  cal- 
cium cyanamide,  37,  38. 

Florida,  storage  test  in,  24,  31. 

Frank,  Dr.  Albert  R.,  3,  85. 

Frank,  Prof.  Adolph,  i. 

Freudenberg,  Herman,  3. 

Fungi  —in  decomposition  of  cyana- 
mide, 35,  36. 

Germination,  effect  of  Cyanamid 
on,  82. 

Glass  sand,  effect  on  cyanamide 
decomposition,  52,  53,  54. 

Glucose — effect  in  decomposition  of 
cyanamide,  34-36. 

Granulated  Cyanamid,  7  ;  activity 
compared  with  that  of  powdered 
Cyanamid,  92,  availability  of, 
96-99;  solubility  of,  95-96. 

Guanidine,  9. 

Gunning  method  in  Cyanamid  an- 
alysis, 19. 

Hall,  A.  D.,  60. 

Haloid  acids,  12. 

Hardening  powders,  9. 

Haselhoff,  E.,  73. 

Hazard,  fire  and  water,  of  Cyana- 
mid, 102-106. 

Headden,  72. 

Heat,  effect  of  on  Cyanamid,  102- 
106. 

Heat,  effect  on  conversion  of  dical- 
cium  to  tricalcium  phosphate 
91,  92. 

Heating  soil,  effect  on  cyanamide 
decomposition,  49. 

Henschel,  G.,  11,  22— decomposi- 
tion products  in  exposed  Cyana- 
mid, 30,  31. 


no 


INDEX 


History  of  Cyanainid  industry,  i. 

Hutchinson,  6i. 

Hydrogen,  effect  on  cyanamide 
conversion,  47. 

Hydrogen  sulphide,  action  on  cyan- 
amide,  12. 

Hydrolysis  of  cyanamide  salts,  14, 

Increase  in  weight  during  storage, 
24-31,  85. 

Intensit,  9. 

Inouye,  R.,  77,  78. 

Iron  hydroxide,  effect  on  cyana- 
mide decomposition,  54,  55. 

Iron  ore,  effect  on  cyanamide  de- 
composition, 52,  53,  54. 

Iron  oxide,  effect  on  cyanamide  de- 
composition, 52,  53. 

Jacksonville,   Fla.,  storage  test  at, 

24,  31- 

Jacoby,  10. 

Kalkstickstoff,  definition,  4. 

Kaolin,  effect  on  cyanamide  de- 
composition. 52,  53. 

Kappen,  H.,  32  ;  experiments  with 
soil,  34 ;  experiments  with  col- 
loidal substances,  51-59 ;  effect  of 
acetylene,  73;  value  of  dicyandia- 
mide,  77. 

Kjeldahl  method,  suitable  for 
Cyanamid  nitrogen  determina- 
tion, 19. 

Kloppel,  J.,  86. 

Ivarge  applications  of  fertilizer,  69, 
72. 

Laterite  earth,  effect  on  cyanamide 
decomposition,  52,  53. 

Liberi,  G.,  76. 

Lime,  action  on  cyanamide,  13,  36. 
See  also  Calcium,  calcium  hy- 
droxide. 

Lime-nitrogen,  definition,  3. 

Liquid  air,  source  of  nitrogen,  5, 

Lohnis,  77. 

Manganese  dioxide,  effect  on  cyan- 
amide decomposition,  52,  53. 


Manganese  hydroxide,  effect  on 
cyanamide  decomposition,  54. 

Mehner,  Prof.  H.,  i. 

Melamine,   12,  15. 

Mellon,  12. 

Metallurgy,  use  of  Cyanamid  in,  9. 

Methylamine  from  cyanamide,  13. 

Miller,  N.  H.  J.,  61. 

Milo,  C.  J.,  77,  80,  81. 

Mixed  fertilizers,  Cyanamid  in, 
89-94. 

Modified  alkaline,  permanganate 
method,  98-101. 

Moissan,   i. 

Moisture,  effect  on  Cyanamid  in 
storage,  24-31. 

Moor  soils,  fertilizers  on,  70,  74. 

Miintz,  63,  86, 

Mustard,  destruction  with  lime- 
nitrogen  in  oat  fields,  86. 

Neutralizing  properties  of  Cyana- 
mid, 91-94. 

Neutral  permanganate  method,  96- 

lOI. 

Niagara  Falls,  Ontario,  storage 
test  at,  25-27. 

Nitrate  nitrogen — preventing  loss 
by  use  of  Cyanamid,  93. 

Nitrates,  effect  on  analysis  of  Cyan- 
amid, 19 ;  effect  on  cyanamide 
decomposition,  48. 

Nitric  acid,  action  on  cyanamide, 
12  ;  effect  on  cyanamide  decom- 
position, 48 ;  manufacture  from 
lime-nitrogen,  8  ;  preventing  loss 
of  in  fertilizer  mixtures,  93,  94. 

Nitrification,  in  acid  soils,  83  ;  of 
Cyanamid  compared  with  am- 
monium sulphate,  dried  blood, 
etc.,  62-64. 

Nitrites,  action  on  cyanamide,  13. 

Nutritive  substances,  effect  of  pres- 
ence in  cyanamide  decomposi- 
tion, 32-36,  81. 


INDEX 


III 


Nitrogen,  analysis  of  in  Cyan  amid, 
19,  20  ;  duration  of  Cyanamid  in 
soil,  64  ;  excessive  applications 
of.  69-73;  fixation  of  as  Cyanamid, 
1-8  ;  prevention  of  loss  as  nitrate 
nitrogen,  93. 

Nitro-guanidine,  9. 

Nitrolim,  definition,  4. 

Nomenclature,  3. 

Nottin,  63,  86. 

Nuckolls,  A.  H.,  102. 

Oat-fields— destruction  of  wild  mus- 
tard in,  86. 

Oats,  excessive  applications  of  ni- 
trogen on,  69. 

Oil  in  Cyanamid,  7,  104. 

Old  Cyanamid,  compounds  in,  28. 

Ostwald  Process,  8. 

Oxidizing  agents,  action  on  cyana- 
mide,  13. 

Patents,  Cyanamide,  3. 

Penicillum  brevicaule,  in  decom- 
position of  cyanamide,  35,  36. 

Permanganate  ;  potassium  —  effect 
on  Cyanamid,  95-101. 

Perotti,  77. 

Phosphates  —mixtures  with  Cyana- 
mid, 91-94. 

Phosphoric  acid,  action  on  cyana- 
mide, 12. 

Play  fair,  i. 

Poison,  definition  of,  65. 

Potassium  hydroxide,  effect  on 
cyanamide  decomposition,  48. 
See  also  alkalies. 

Potassium  permanganate,  effect  on 
Cyanamid,  95-101. 

Power  consumption,  in  Cyanamid 
manufacture,  7. 

Preparation  of  cyanamide,  10. 

Pressure  of  nitrogen  tk  Cyanamid 
formation,  6. 

Properties  of  cyanamide,  10-18. 

Pure  substances  and  toxicity,  80. 


Quantity  of  Cyanamid  to  apply  as 
fertilizer,  88. 

Rate  of  removal  of  cyanamide  from 
soil  solution,  39. 

Reducing  agents,  action  on  cyana- 
mide, 13,  99. 

Reis,  36. 

Retention  of  Cyanamid  nitrogen  in 
soil,  60. 

Reversion  in  acid  phosphate — 
Cyanamid  mixtures,  91. 

Root  crops,  86. 

Rothe,  F.,  2. 

Sabaschnikoff,  77,  80. 

Sackett,  72. 

Sand,  effect  on  cyanamide  decom- 
position, 52.  53. 

Schiick,  10. 

Schneidewind,  86. 

Second  and  third  stages  of  Cyana- 
mid decomposition  in  soil   38. 

"Secondary  products,"  effect  on 
cyanamide  decomposition,  33, 
34,  81. 

Sidgwick,  II. 

Siemens  &  Halske,  i. 

Silicates,  effect  on  cyanamide  de- 
composition, 49,  50. 

Silicic  acid,  effect  on  cyanamide 
decomposition,  54. 

Silver  cyanamide,  17. 

Sodium  acid  cyanamide,  13. 

Sodium  cyanamide,  10,  13. 

Sodium  nitrate,  excessive  applica- 
tions, 69. 

Soil,  decomposition  of  Cyanamid 
in,  32-59. 

Soil  solution,  rate  of  removal  of 
cyanamide  from,  39. 

Sol,  iron  oxide,  effect  on  cyana- 
mide decomposition,  56. 

Solubility  of  Cyanamid,  95-101. 

Solution  of  cyanamide,  changes  in, 
14,  15,  16,  76;  rate  of  solution  of 
Cyanamid,  96. 

Steglich,  86. 


112 


INDEX 


Sterile  conditions  and  cyanamide 
decomposition,  33,  40,  43,  44,  50, 

51,  56,  57. 
Sterilization  of  soil,  eflfect  on  cyana- 
mide decomposition,  44,  50,  56, 

57. 

Stickstoffkalk,  definition,  4. 

Storage  of  Cyanamid,  variation  of 
nitrogen  during,  24-31. 

Strohmer,  85. 

Stutzer,  36. 

Substitution  compounds  of  cyana- 
mide, 13. 

Sugar  beets,  85,  86. 

Sulphuric  acid,  action  on  cyana- 
mide,  12. 

Summary  on  cyanamide  decom- 
position in  soil,  57-59. 

Surrogate,  8. 

Temperature,  effect  on  cyanamid 
decomposition  in  soil,  43,  44  ;  re- 
action temperature,  barium  cy- 
anamide, 2  ;  calcium  cyanamide, 
2,  6. 

Tempering  powders,  9. 

Thio-urea,  12. 

Top-dressing,    use    of    Cyanamid 
as,  87. 

Toxicity  :  of  cyanamide,  34-36  ;  of 
fertilizers,  65-82. 


Tri-calcium  phosphate  in  Cyanamid 
mixtures,  91,  92. 

Tricyantriamide,  12. 

Ulpiani,  C,  chemistry  of  cyana- 
mide, 12,  14,  16,  22,  23;  decom- 
position of  Cyanamid  in  soil, 
32-51,  57.  59;  dicyandiamide, 
34,  77. 

Umber,  effect  on  cyanamide  decom- 
position, 52,  53- 

Underwriters' Laboratories,  102-106. 

Urea,  assimilation  of,  60 ;  deter- 
mination of,  22 ;  formation  from 
cyanamide,  12,  15,  37,  43,  44,  51, 
89  ;  manufacture,  9 ;  transforma- 
tion by  bacteria,  40,  44,  57. 

Volatility  of  calcium  cyanamide,  6. 

Water :  Effect  on  Cyanamid  in 
storage,  24-31 ;  hazard  of  in  fires, 
103,  105,  106  ;  hydrolysis  of 
cyanamide  salts  in,  14 ;  solu- 
bility of  Cyanamid,  95-101. 

Weeds,  destruction  with  lime-ni- 
trogen, 86,  87. 

Weight,  increase  during  storage  of 
Cyanamid,  24-31,  85. 

Wheat,  86. 

Willson,  I. 

Zeolites,  effect  on  cyanamide  de- 
composition, 49,  50. 


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